Distinct subregions of Swi1 manifest striking differences in prion transmission and SWI/SNF function.
We have recently reported that the yeast chromatin-remodeling factor Swi1 can exist as a prion, [SWI(+)], demonstrating a link between prionogenesis and global transcriptional regulation. To shed light on how the Swi1 conformational switch influences Swi1 function and to define the sequence and structural requirements for [SWI(+)] formation and propagation, we functionally dissected the Swi1 molecule. We show here that the [SWI(+)] prion features are solely attributable to the first 327 amino acid residues (N), a region that is asparagine rich. N was aggregated in [SWI(+)] cells but diffuse in [swi(-)] cells; chromosomal deletion of the N-coding region resulted in [SWI(+)] loss, and recombinant N peptide was able to form infectious amyloid fibers in vitro, enabling [SWI(+)] de novo formation through a simple transformation. Although the glutamine-rich middle region (Q) was not sufficient to aggregate in [SWI(+)] cells or essential for SWI/SNF function, it significantly modified the Swi1 aggregation pattern and Swi1 function. We also show that excessive Swi1 incurred Li(+)/Na(+) sensitivity and that the N/Q regions are important for this gain of sensitivity. Taken together, our results provide the final proof of "protein-only" transmission of [SWI(+)] and demonstrate that the widely distributed "dispensable" glutamine/asparagine-rich regions/motifs might have important and divergent biological functions.
Du
Zhiqiang
Z
Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Searle 5-474, MC S205, 320 E. Superior Street, Chicago, IL 60611, USA.
Crow
Emily T
ET
Kang
Hyun Seok
HS
Li
Liming
L
D020816:Amino Acid Motifs / Q000235:genetics; D000682:Amyloid / Q000378:metabolism; D001216:Asparagine / Q000235:genetics / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D002872:Chromosome Deletion; D015825:Chromosomes, Fungal / Q000235:genetics; D005973:Glutamine / Q000235:genetics / Q000378:metabolism; D015151:Immunoblotting; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009154:Mutation; D011328:Prions / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D000682:Amyloid; D002868:Chromosomal Proteins, Non-Histone; D008164:Luminescent Proteins; D011328:Prions; C445179:SWI-SNF-B chromatin-remodeling complex; C078562:SWI1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D005973:Glutamine; D001216:Asparagine