Worm Breeder's Gazette 12(3): 58 (June 15, 1992)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Update on the Cloning of mei-1

Shawna Clark-Maguire, Paul E. Mains

Department of Medical Biochemistry, University of Calgary, Alberta, Canada

The maternally-expressed gene mei-1 has mutations that affect either meiosis or mitosis. Loss-of-function mutations prevent the formation of the meiotic spindle while a gain-of-function allele disrupts the first mitotic cleavage. These two classes of mutations show a complex pattern of genetic interactions with each other as well as with mutations in several interacting genes.

We have cloned mei-1 using the usual tricks involving the physical map and transformation rescue; both genomic and cDNA clones have been sequenced. The sequence shows some curious similarities to other genes, but their significance is not clear (identities are about 35% over 250 amino acids). Perhaps the most interesting similarity is to the CDC48 gene of Saccharomyces. Mutations of this gene block division prior to spindle-pole body separation; perhaps this is analogous to the failure of meiotic spindle formation of mei-1 (lf) alleles. Other genes similar to mei-1 ,also from Saccharomyces, are SEC 18, involved in vesicle trafficking, and PAS1 ,implicated in peroxisome formation. Perhaps there is a role for vesicles in spindle formation. However, the human gene TBP-1 ,which binds the TAT gene of HIV and regulates transcription, shows the same degree of similarity. Genes, of unknown function, from pig and Xenopus, are also similar to mei-1 .

One common feature these proteins are likely to share is nucleotide binding. Even though consensus sequences proposed for ATP binding sites are very loose, the mei-1 -likegenes are strongly conserved in this region, well beyond that of the proposed consensus sequences. Indeed, the purified Xenopus protein shows in vitro ATPase and GTPase activities. Perhaps mei-1 is a member of a conserved family of ATPases. Two additional C. elegans family members were among the sequences reported by the cDNA sequencing project (WBG 12(2): 26); these may represent some of our genetically identified interacting genes.

The gene density in the mei-1 region is fairly high: the beta subunit of casein kinase II is ~3 kb and lin-10 is ~8 kb from the 5' end of mei-1 while an uncharacteristic gene (identified by a cDNA isolated with a mei-1 genomic clone) is immediately 3'. This latter gene is convergently transcribed with mei-1 and the poly A sites of the two genes are only 10 base pairs apart. There is a hot-spot for recombination in this area; the two-factor distance between mei-1 and lin-10 is 0.3 cM, leading to an estimate of about 50 cM/kb, 30 times higher than Sulston et al. (Nature 356:37) have recently reported for the centre of LG III ( mei-1 is in the cluster of LG I). The amount of recombination seems to fall off on either side of this region: to the left ( lin-10 to unc-13 )it is approximately 1000 kb/cM while to the right ( mei-1 to unc-120 )it is about 500 kb/cM. Based upon the behavior of deficiencies with endpoints near mei-1 and lin-10 ,McKim and Rose also showed that this region is important for recombination

Literature Cited:

1991 Meeting abstracts, p. 212

WBG 12(2): 26

Sulston et al. Nature 356:37