We thank Sohini Chakrabortee, Sandra Jones, David Garcia, Bhupinder Bhullar, Amelia Chang, Richard She, and Susan Lindquist for their assistance in developing the assays used in this paper, as well as the reviewers for their thoughtful comments.

1. Initial Overexpression
<ol>
	<li>Transform the yeast cells (in this case, BY4741 MAT a haploids) previously grown in YPD liquid (10 g of yeast extract, 20 g of peptone, and 20 g of glucose per 1 L) with the desired candidate constructs from the FLEXGene ORFeome library (yeast ORFs under the control of a galactose-inducible promoter in the URA3-marked centromericplasmid backbone, pBY01129).</li>
	<li>Use autoclaved toothpicks to pick four separate colonies from these...

<ol>
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The authors have nothing to disclose.

The first yeast prions were identified by their unusual phenotypes and perplexing patterns of inheritance. The characteristics of these prions were then used to build algorithms and computational tools to screen for additional prion proteins. The method described here, in contrast, is experimental and relies on transient overexpression to create a lasting change-a stable state-encoded in protein conformation. However, if the efficiency of &#34;seeding&#34; prion assembly by overexpression for any given protein is very lo...

Biological systems frequently experience transient fluctuations in protein abundance. Whether these have a lasting impact in shaping the phenotype of an organism or of future generations remains unclear. The best-known instances of this biology involve a rare class of proteins, prions, which drive the emergence of heritable traits without genome modification. Instead, these proteinaceous and infectious particles transmit phenotypes via self-perpetuating changes to protein conformation1,2. This type of inheritance was discovered as the cause of the unusual inheritance patterns of a devastating neurodegenerative disease. However, studies in organisms ranging from fungi to mammals3,4,5,6,7,8,9,10 have since revealed that prion-like elements can confer adaptive value. Nonetheless, prions have been viewed as a fascinating but rare biological oddity.
This prevailing wisdom is in part held because the characterization of protein-based inheritance has long been restricted by a small set of examples. Recent systematic screening efforts have widened this picture significantly by identifying several new bona fide prions11 and almost two dozen protein domains12 with the capacity to fuel prion-like conformational conversion. However, because these approaches have generally focused on strong amino acid sequence biases, the prions that have been discovered share the biochemical properties of the founding yeast prions [PSI+]13,14, [URE3]15, and [RNQ+]11,16. These include: 1) modular domains that are rich in long polymeric stretches of asparagine (N) and glutamine (Q), 2) assembly into an amyloid [PRION+] conformation17,18,19, and 3) complete reliance on disaggregase Hsp104 function for faithful propagation from mother to daughter13,20,21. Indeed, many bona fide prions, including [GAR+], [Het-s], and even the original prion (PrPSc), would be missed under such stringent criteria. Perhaps more importantly, they would be unable to capture any novel mechanisms of protein-based inheritance22. Thus, the true biological breadth of such phenomena may be far more common in nature than previously assumed.
To investigate this question, a high-throughput, proteome-wide strategy was employed. A hallmark of all prions, including PrPSc, [GAR+], and [Het-s], is that the transient overexpression of the causal proteins strongly increases the rate of prion acquisition15,23,24,25,26. We took advantage of this feature to systematically ask, across the entire yeast ORFeome, if stable protein-based, epigenetic states could be initiated by transiently inducing the overexpression of individual proteins. It is well known that protein overexpression can alter phenotypes27. However, prion proteins are unusual because their temporary overproduction produces a change in phenotype that is heritable for many hundreds of generations after the initial overexpression. We previously took advantage of this feature, as well as the unusual inheritance patterns of protein-based genetic elements, to identify dozens of proteins that are capable of heritably re-wiring phenotypic landscapes without altering the genome28. Although some identified proteins were previously known as prions, most were not, underscoring the power of this approach to uncover new forms of protein-based inheritance.

<table width="958">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="width:356px;height:21px;">Guanidine hydrochloride</td>
			<td style="width:299px;">Sigma</td>
			<td style="width:125px;">Cat#G3272-25G</td>
			<td style="width:179px;">Chemical</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Manganese chloride</td>
			<td>Sigma</td>
			<td>Cat#M8054-100G</td>
			<td>Chemical</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethidium bromide</td>
			<td>Sigma</td>
			<td>E1510</td>
			<td>Chemical</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">5-Fluoroorotic Acid</td>
			<td>Sigma</td>
			<td>Cat#F5013-50MG</td>
			<td>Chemical</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BY4741 MATa (his3&#916;1 leu2&#916;0 LYS2 met15&#916;0 ura3&#916;0)</td>
			<td>Winston et al., 1995; Brachmann et al., 1998</td>
			<td>N/A</td>
			<td>Yeast strain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BY4741 MAT&#945; (his3&#916;1 leu2&#916;0 lys2&#916;0 MET15 ura3&#916;0)</td>
			<td>Winston et al., 1995; Brachmann et al., 1998</td>
			<td>N/A</td>
			<td>Yeast strain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hsp70 (K69M)&#160;</td>
			<td>Jarosz et al., 2014b</td>
			<td>N/A</td>
			<td>Plasmid</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FLEXGene library</td>
			<td>Hu et al., 2007</td>
			<td>N/A</td>
			<td>Plasmid library</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dextrose (glucose)</td>
			<td>Fisher Scientific</td>
			<td>D16-3</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Raffinose</td>
			<td>Sigma</td>
			<td>R0250-25G</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Galactose</td>
			<td>Fisher Scientific</td>
			<td>BP656-500</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CSM</td>
			<td>Sunrise Science</td>
			<td>1001-100</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CSM-URA</td>
			<td>Sunrise Science</td>
			<td>1004-100</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CSM-LYS</td>
			<td>Sunrise Science</td>
			<td>1032-100</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CSM-MET</td>
			<td>Sunrise Science</td>
			<td>1019-100</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CSM-LYS-MET</td>
			<td>Sunrise Science</td>
			<td>1035-100</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">yeast extract</td>
			<td>Fisher Scientific</td>
			<td>BP1422-2</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">peptone</td>
			<td>Research Products International</td>
			<td>P20240-5000</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">bacto-peptone</td>
			<td>BD</td>
			<td align="right">211677</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">glycerol</td>
			<td>EMD Millipore</td>
			<td>GX0185-2</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">yeast nitrogen base w/o amino acids</td>
			<td>BD</td>
			<td align="right">291920</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">agar</td>
			<td>IBI Scientific</td>
			<td>IB49172</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Adenine sulfate</td>
			<td>Sigma</td>
			<td>A3159-25G</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Potassium acetate</td>
			<td>Sigma</td>
			<td>P1190-500G</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Uracil</td>
			<td>Sigma</td>
			<td>U0750-100G</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Histidine</td>
			<td>Sigma</td>
			<td>H8000-100G</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Leucine</td>
			<td>Sigma</td>
			<td>L8000-25G</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Lysine</td>
			<td>Sigma</td>
			<td>L5501-25G</td>
			<td>Media component</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RNase I&#160;</td>
			<td>Thermo Fisher Scientific</td>
			<td>EN0601</td>
			<td>Enzyme</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">biotinylated DNase</td>
			<td>Thermo Fisher Scientific</td>
			<td>AM1906</td>
			<td>Enzyme</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">zymolyase 100T (yeast lytic enzyme)</td>
			<td>Sunrise Science</td>
			<td>N0766555</td>
			<td>Enzyme</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microplate reader</td>
			<td>BioTek</td>
			<td>Synergy H1</td>
			<td>Equipment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microplate stacker</td>
			<td>BioTek</td>
			<td>BioStack3</td>
			<td>Equipment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plate filler</td>
			<td>BiotTek</td>
			<td>EL406</td>
			<td>Equipment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Liquid handling robot</td>
			<td>Beckman Coulter</td>
			<td>Biomek FX</td>
			<td>Equipment</td>
		</tr>
	</tbody>
</table>

high-throughput screening for protein-based inheritance in s. cerevisiae

The encoding of biological information that is accessible to future generations is generally achieved via changes to the DNA sequence. Long-lived inheritance encoded in protein conformation (rather than sequence) has long been viewed as paradigm-shifting but rare. The best characterized examples of such epigenetic elements are prions, which possess a self-assembling behavior that can drive the heritable manifestation of new phenotypes. Many archetypal prions display a striking N/Q-rich sequence bias and assemble into an amyloid fold. These unusual features have informed most screening efforts to identify new prion proteins. However, at least three known prions (including the founding prion, PrPSc) do not harbor these biochemical characteristics. We therefore developed an alternative method to probe the scope of protein-based inheritance based on a property of mass action: the transient overexpression of prion proteins increases the frequency at which they acquire a self-templating conformation. This paper describes a method for analyzing the capacity of the yeast ORFeome to elicit protein-based inheritance. Using this strategy, we previously found that &gt;1% of yeast proteins could fuel the emergence of biological traits that were long-lived, stable, and arose more frequently than genetic mutation. This approach can be employed in high throughput across entire ORFeomes or as a targeted screening paradigm for specific genetic networks or environmental stimuli. Just as forward genetic screens define numerous developmental and signaling pathways, these techniques provide a methodology to investigate the influence of protein-based inheritance in biological processes.

Protein overexpression is known to dramatically alter cellular phenotypes27. Indeed, with an initial screening approach, hundreds of new phenotypes were reproducibly recovered from the overexpression of clones from the yeast ORFeome using just ten stressors. However, the assays described above allow for the assessment of whether cells retain any long-term stable phenotypes following this overexpression. One protein capable of encoding such a state is Psp1. Psp1 is ...

Watch this Scientific Journal Video about High-throughput Screening for Protein-based Inheritance in S. cerevisiae at JoVE.com

High-throughput Screening for Protein-based Inheritance in S. cerevisiae

This protocol describes a high-throughput methodology to functionally screen for protein-based inheritance in S. cerevisiae.

High-throughput Screening for Protein-based Inheritance in S. cerevisiae

The encoding of biological information that is accessible to future generations is generally achieved via changes to the DNA sequence. Long-lived ...

The overall goal of this high-throughput yeast phenotyping is to screen for proteins that illicit a lasting phenotypic memory of passed over expression, as a proxy for protein-based inheritance. This method can help answer key questions in the yeast Prion field, such as, how many proteins can it illicit inheritance of this type. The main advantage of this technique is that you can screen many proteins and pathways in an unbiased fashion.Start this procedure by growing the appropriate yeast cells in a 96 well plate at 30 degrees celsius, as described in the text protocol. Visually inspect the cultures to confirm that the cultures are saturated, cells should be visible by eye, at the bottom of each well. Use a liquid handling robot to prepare 384 well plates, containing 45 microliters of the appropriate medium per well.First, dispense Scal-URA into the wells of a 384 well plate. Then dispense Scal-URA plus the stressor of interest into the wells of a second plate, 20 millimolar of manganese chloride is used as the stressor in this experiment. Thirdly, dispense SD-URA, which will not induce plasmid expression, plus manganese chloride into another plate.Lower the 96 well plate containing the cultures onto the liquid handling robot and inoculate a one to four array of one microliter from each well of the 96 well plate, into four separate wells of each 384 well plate filled with a different media. Immediately place the plates with cells on a microplate stacker at room temperature and atmospheric carbon dioxide. Set the protocol for a 72 hour continuous loop, measuring the optical density at 600 nanometers with the microplate reader.After the growth measurements, transfer one microliter per well of the SCal-URA induced cultures that experienced protein over-expression to new 384 well plates, containing 45 microliters per well of ST-URA medium that does not permit protein expression of the plasmid. In parallel, perform analogous inoculations of a second set of 384 well plate containing 45 microliters per well of ST-URA from the cultures that were grown in ST-URA in the presence of the stressor. Place the plates in a humidified chamber and grow the plates for 48 hours at 30 degree celsius to saturation.After 48 hours, use the plates to re-inoculate one microliter per well in 384 well plates containing 45 microliters per well of ST-URA. Then, perform a separate re-inoculation of one microliter per well from the same source plate into a separate 384 well plate containing 45 microliters per well of ST-URA with the stressor. Immediately place the plates with cells of the microstacker at room temperature and atmospheric carbon dioxide and set the protocol for a 48 hour continuous loop, measuring the optical density at 600 nanometers with a microplate reader.When the growth measurements are complete, use the plate reader software to export the time versus optical density at 600 nanometer measurements as an XY table. Group columns of the optical density measurements for each biological replicate together and calculate the mean. Create an XY plot of time versus optical density at 600 nanometers to generate growth curves.For cultures that chose significant growth differences in response to a given stressor, dependent upon ancestral protein over-expression, take one microliter from each biological replicate, dilute in 10 milliliters of water and then plate 50 microliters on plates containing 5-FOA. Grow at 30 degree celsius for three days. If this results in too many or too few colonies per plate, adjust the dilution factor accordingly.100 to 200 colonies per plate is ideal. Pick eight to 32 single colonies with autoclave toothpicks and pin them to 96 well plates containing 150 microliters of SDCSM per well. Place the plates in a humidified chamber and grow to saturation for 48 to 72 hours at 30 degrees celsius.Use these cultures to inoculate two new sets of 96 well plates containing 150 microliters per well of SDCSM, both with and without the stressor. Place the plates on a microplate stacker and set the protocol to measure the optical density at 600 nanometers on a 48 hour continuous loop. After 48 hours, analyze the data as shown earlier and confirm that the significant growth differences seen earlier, are maintained after plasmid loss.The cells that maintain the induced phenotypes are then tested for classic hallmarks of protein-based inheritance as described in the text protocol. This protein-based inheritance screen revealed the transient over-expression of the PSP1 open reading frame, drives a resistance to manganese chloride that was maintained for hundreds of generations in cells, long after over-expression had ceased. Prion predicting algorithms scored the end terminus of PSP1 as moderately Prion-like.In contrast, the algorithms predicted virtually no significant Prion-like sequence features from most inducing proteins recovered on the screen, as shown by this representative analysis. Growth measurements of strains and SDCSM with manganese chloride, normalized to a corresponding naive PSP1 minus control, indicated that inhibition of the HSP104 disaggregase does not impair PSP1 dependent manganese chloride resistance whereas the removal of the HSP70 chaperone and the PSP1 gene, heritably eliminates this phenotype. All spores from single tetrads of crosses between strains, harboring the PSP1 dependent phenotypic state and naive strains, display manganese chloride resistance, indicating non-mendelian inheritance of the phenotype.A comparison of the infectivity for protein transformation between mock lysates and PSP1 harboring lysates as the transmissible material, showed that over 53%of naive cells transformed with seeded PSP1, received the corresponding manganese chloride resistance phenotype. Once mastered, this technique can be done in a couple of weeks, including incubation steps and the preparation of most screening steps can be done in less than two hours per day, even with a large number of plates. While attempting this procedure, it is important to remember to plan exactly what you wanna test beforehand and keep in mind the scale of the experiment.Now this is especially important to beginners of the technique. Following this procedure, other methods like those described in the text protocol can be performed to determine if the phenotypes observed in the screening display a true, Prion-like pattern of inheritance. After its development, this technique paved the way for researchers in the field of epigenetics to explore the breadth of Prion biology in sacralis service CI.After watching this video, you should have a good understanding of how to design a high throughput screen for new forms of protein-based inheritance in yeast, in both an unbiased and targeted fashion.Don't forget, that certain chemical stressors such as DNA damaging agents can be extremely hazardous and precautions, such as wearing personal protective equipment, should always be taken while performing this procedure.

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6.2K Görüntüleme.  Stanford University School of Medicine. The overall goal of this high-throughput yeast phenotyping is to screen for proteins that illicit a lasting phenotypic memory of passed over expression, as a proxy for protein-based inheritance. This method can help answer key questions in the yeast Prion field, such as, how many proteins can it illicit inheritance of this type. The main advantage of this technique is that you can screen many proteins and pathways in an unbiased fashion.Start this procedure by growing the appropriate y...