High impact information on CHC1

• Actin, myosin 2, and clathrin heavy chain are involved in mating partner discrimination, since strains carrying mutations in the genes encoding these proteins result in a small but significant defect in mating partner discrimination [1].
• Even in the presence of the suppressor gene, mutants lacking the clathrin heavy chain grow slowly, are genetically unstable, are morphologically abnormal, and show loss of or reduction in several yeast functions [2].
• Sec17 also shares structural features with HEAT and clathrin heavy chain repeats [3].
• Here, we have found that disruptions in the genes encoding a dynamin-related protein (VPS1) or clathrin heavy chain (CHC1) abolish HDSV production, yielding LDSVs that contain all secreted cargos [4].
• The drs2 null allele is also synthetically lethal with clathrin heavy chain (chc1) temperature-sensitive alleles, but not with mutations in COPI subunits or other SEC genes tested [5].

Biological context of CHC1

• Plasmids from six distinct genetic loci, none of which encoded CHC1, were recovered [6].
• CDC55 maps between CDC43 and CHC1 on the left arm of chromosome VII [7].
• Light chain-deficient cells showed phenotypes similar to those displayed by yeast that have a disruption in the clathrin heavy chain gene (CHC1) [8].
• To further understand the molecular mechanisms underlying clathrin-mediated protein transport pathways, we initiated a genetic screen for mutations that display synthetic growth defects when combined with a temperature-sensitive allele of the clathrin heavy chain gene (chc1-521) in Saccharomyces cerevisiae [9].
• Phospholipid endocytosis was also independent of the gene encoding the clathrin heavy chain, CHC1 [10].

Anatomical context of CHC1

• Cells carrying deletions of the CHC1 gene (chc1 delta) also sorted CPY to the vacuole even when subjected to temperature shifts [11].
• These conclusions clarify previous studies of chc1 delta cells which raised the possibility that clathrin is not involved in vacuolar protein sorting [11].
• Surprisingly, we found that a significant fraction of Mnn1p is mislocalized to the plasma membrane in a clathrin heavy chain temperature sensitive mutant while guanosine diphosphatase remains intracellular [12].
• Clathrin-coated vesicle assembly and disassembly is regulated by some 30 adaptor and accessory proteins, most of which interact with clathrin heavy chain [13].
• We find that CPY transport is mediated by the endosome and requires normal trafficking of its sorting receptor, Vps10p, the steady state distribution of which is not altered in chc1 cells [14].

Associations of CHC1 with chemical compounds

• The proline-rich domain was shown to bind to two proteins, including clathrin heavy chain, Chc1p [15].
• A strain of scd1-i genotype carrying the clathrin heavy-chain gene under GAL1 control (GAL1:CHC1) was transformed with a YEp24 yeast genomic library, and colonies that could grow on glucose were selected [6].

Physical interactions of CHC1

• In contrast, inactivation of the clathrin heavy-chain gene CHC1 results in transport of Kex2p and other Golgi membrane proteins to the cell surface [16].
• Surprisingly, strains harboring chc1-5 exhibited a significant defect in transport of carboxypeptidase Y or carboxypeptidase S to the vacuole that was not observed in other chc1 ts mutants [17].
• Cells expressing the S(all)A mutant Clc1p displayed no defects in Clc1p binding to clathrin heavy chain, clathrin trimer stability, sorting of a soluble vacuolar protein, or receptor-mediated endocytosis of mating pheromone [18].

Regulatory relationships of CHC1

• By constructing strains in which CHC1 expression is regulated by the GAL10 promoter, we demonstrate that the lethal alleles of SCD1 and CDL1 are recessive [19].
• However, deletion of APM1 greatly enhanced the temperature-sensitive growth phenotype and the alpha-factor processing defect displayed by cells carrying a temperature-sensitive allele of the clathrin heavy chain gene [20].

Other interactions of CHC1

• Here, the relationship of the two localization defects was assessed by examining the effects of a temperature-sensitive CHC1 allele on trafficking of wild-type (WT) and TLS mutant forms of Kex2p [16].
• If CHC1 was overexpressed in clc1-delta cells, heavy chain trimers were detected and several clc1-delta phenotypes were partially rescued [8].
• However, aps1 delta accentuated the slow growth and alpha-factor pheromone maturation defect of cells carrying a temperature-sensitive allele of clathrin heavy chain (Chc) (chc1-ts) [21].
• This genetic interaction between arf1 and chc1 provides in vivo evidence for a role for ARF in clathrin coat assembly [17].
• 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 [6].

References