The yeast homolog to mouse Tcp-1 affects microtubule-mediated processes.

Abstract

A Saccharomyces cerevisiae homolog to Drosophila melanogaster and mouse Tcp-1 encoding taiDless complex polypeptide 1 (TCP1) has been identified, sequenced, and mapped. The mouse t complex and many of its unusual properties have attracted the attention of geneticists for nearly 60 years (11,12,20,60). t alleles were first discovered by their interaction with a dominant T-locus mutation to produce a tailless phenotype in double heterozygous T/t animals. Heterozygous T/+ animals have a short tail, and homozygous T/T animals are embryonic lethals. Homozygous tx/tY males are sterile (37, 38), and heterozygous +/t animals have tails of normal length and are visually indistinguishable from normal wild-type +/+ animals. Compared with wild-type laboratory chromosome 17, the principal variation in t chromosomes consists of at least four inversions of about 1% of the mouse genome (30 Mbs of DNA) (21, 23). The t complex is the name given to the rearranged region. It contains about 100 genes (39), including several genes expressed in the testes whose products show t-allele-specific alterations.t chromosomes confer a number of effects, including disturbances of embryonic development, alterations of sperm differentiation and function, and transmission ratio distortion. While transmission of the t complex through females is normal, heterozygous t/+ males transmit the t-bearing chromosome to their progeny in excess of the Mendelian expectation. Genetic analysis of transmission ratio distortion suggests that it depends on the action of up to four distorter loci (Tcd-J to Tcd4) as well as a responder locus (Tcr) (2, 36-38, 56, 63). The molecular basis of transmission ratio distortion remains unknown.A number of candidate genes for the distorter and responder loci, including Tcp-1, have been isolated from the t complex (75). Tailless complex polypeptide 1 (TCP-1), a protein of 57 kDa, is expressed in large amounts during * Corresponding author.

Intracellular localization of a group II chaperonin indicates a membrane-related function

“…There are previous reports that HSP60s in bacteria and mitochondria, which form group I chaperonins, are membrane associated (33)(34)(35)(36)(37). There are also reports that the HSP60-related TCP1s in eukarya, which form group II chaperonins (known as CCT or TriC), are membrane associated (38)(39)(40)(41). We recently discovered that in human red blood cells TCP1 is predominantly cytoplasmic under normal conditions, but after heat treatment it relocates to the membrane (C. T. Wagner, I. Y. Lu, M. H. Hoffman, W. Q.…”

Heat‐shock proteins as molecular chaperones

“…Subsequent to the cloning of the mouse TCPl gene (Willison et al, 1986), related proteins from Drosophilu (Ursic and Ganetzky, 1988) and S. cerevisiae (Ursic and Culbertson, 1991) were reported. The unexpected finding that TF55, an abundant protein of the thermophilic bacterium Sulfolobus shibatue, had not only the structural and functional hallmarks of a typical chaperonin but also had a very strong sequence similarity to TCPl lent support to the initial suggestion that TCPl might be a cytoplasmic chaperonin (Trent et al, 1991 In yeast, TCPl is essential for growth ; temperature-sensitive mutants show aberrant mitotic spindle formation (Ursic and Culbertson, 1991). Two independent studies demonstrated that TCPl plays a role in the biogenesis of tubulin and actin (Gao et al, 1992;Yaffe et al, 1992).…”

The JNM1 gene in the yeast Saccharomyces cerevisiae is required for nuclear migration and spindle orientation during the mitotic cell cycle.

“…Other mutants have been identified that also exhibit a nuclear migration defect (Watts et al, 1987;Berlin et al, 1990;Kormanec et al, 1991;Ursic and Culbertson, 1991;McConnell and Yaffe, 1992). The specific role of these genes in nuclear migration is not known and in all cases except numl the nuclear migration defect is only one trait of a more complex phenotype.…”