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Suppressors of clathrin deficiency in Saccharomyces cerevisiae

Nelson, Karen Knokel
http://rave.ohiolink.edu/etdc/view?acc_num=case1058214465

Abstract Details

1995, Doctor of Philosophy, Case Western Reserve University, Molecular Biology and Microbiology.
Clathrin-mediated vesicular transport is important for normal growth of the yeast Saccharomyces cerevisiae. Previously, a genetic locus (SCD1) that influences the ability of clathrin heavy-chain-deficient (Chc-) yeast cells to survive was identified. With the scd1-ν allele, Chc- cells are viable but grow poorly; with the scd1-i allele, Chc- cells are inviable. To identify the SCD1 locus and other genes that can rescue chc1-Δ scd1-i cells to viability, low- and multicopy-suppressor selection strategies were developed. A strain of scd1-i genotype carrying the clathrin heavy-chain under GAL1 control (GAL1:CHC1) was transformed with both a YEp24 and YCp50 yeast genomic library, and colonies that could grow on glucose were selected. Plasmids from five distinct genetic loci (SCD2-SCD6) were recovered from the YEp24 library. Two plasmids with overlapping inserts (A19 and A21) were isolated from the YCp50 library. YEpSCD3 has an overlapping insert with A19 and A21 and is the only suppressor that rescues Chc- scd1-i strains from lethality in low as well as high copy. In this thesis, the characterization of two of these suppressors, SCD2 and SCD5, is described. SCD2 was shown to be UBI4, the polyubiquitin gene. The primary role for ubiquitin is in protein de gradation where conjugation of ubiquitin to cellular acceptor proteins targets these proteins for selective degradation. Since UBI4 is required for survival of cells under stress and is induced during starvation, ubiquitin expression in GAL1:CHC1 cells was examined. After a shift to growth on glucose to repress synthesis of clathrin heavy chains, UBI4 mRNA levels were elevated >10-fold, whereas the quantity of free ubiquitin declined severalfold relative to that of Chc+ cells. This suggests that higher levels of ubiquitin are required for turnover of mislocalized or improperly processed proteins that accumulate in the absence of clathrin and that ubiquitin may play a general role in turnover of proteins in the secretory or endocytic pathway. SCD5 is an essential gene which encodes a novel protein with two regions of repeated motifs. Initial results indicate that Scd5p may be involved in vesicular transport from the trans Golgi network to the plasma membrane.
Sandra Lemmon (Advisor)
176 p.
clathrin deficiency Saccharomyces cerevisiae

Recommended Citations

Citations

  • Nelson, K. K. (1995). Suppressors of clathrin deficiency in Saccharomyces cerevisiae [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1058214465

    APA Style (7th edition)

  • Nelson, Karen. Suppressors of clathrin deficiency in Saccharomyces cerevisiae. 1995. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1058214465.

    MLA Style (8th edition)

  • Nelson, Karen. "Suppressors of clathrin deficiency in Saccharomyces cerevisiae." Doctoral dissertation, Case Western Reserve University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058214465

    Chicago Manual of Style (17th edition)

case1058214465
519
© 1995, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.