A novel cross-phylum family of proteins comprises a KRR1 (YCL059c) gene which is essential for viability of Saccharomyces cerevisiae cells.

We demonstrate here that the open reading frame (ORF) YCL059c, discovered during the systematic sequencing of chromosome III [Oliver et al., Nature 357 (1992) 38-46], codes for a protein essential for yeast: neither spore germination nor cell division occur in strains deleted for this gene. We have cloned the wild-type (wt) gene and shown that it complements the deletion. A relatively abundant RNA transcript corresponds to the gene. The protein has no similarity to proteins of known function. Interestingly, however, it is homologous to several expressed sequence tags (EST) of unknown function from Caenorhabditis elegans, Oryza sativa and Homo sapiens. Thus, a novel family of proteins of presumably nuclear localization, with a characteristic highly basic motif, KRR-R, transcends various phyla, and plays an important role in cellular processes. We propose to call this essential gene KRR1.