Unigenic evolution: a novel genetic model localizes a putative leucine zipper that mediates dimerization of the Saccharomyces cerevisiae regulator Gcr1p

• Published in: Genetics (Austin) Vol. 141; no. 4
• Main Authors: Deminoff, S.J. (University of Southern Mississippi, Hattiesburg, MS.), Tornow, J, Santangelo, G.M
• Format: Journal Article
• Language: English
• Published: 01.12.1995
• Subjects: ADN; MUTACION; MUTACION INDUCIDA; MUTANT; MUTANTES; MUTATION; MUTATION PROVOQUEE; PROTEINAS AGLUTINANTES; PROTEINE DE LIAISON; SACCHAROMYCES CEREVISIAE
• ISSN: 0016-6731; 1943-2631

The GCR1 gene of Saccharomyces cerevisiae encodes a transcriptional activator that complexes with Rap1p and, through UAS(RPG) elements (Rap1p DNA binding sites), stimulates efficient expression of glycolytic and translational component genes. To map the functionally important domains in Gcr1p, we combined multiple rounds of random mutagenesis in vitro with in vivo selection of functional genes to locate conserved, or hypomutable, regions. We name this method unigenic evolution, a statistical analysis of mutations in evolutionary variants of a single gene in an otherwise isogenic background. Examination of the distribution of 315 mutations in 24 variant alleles allowed the localization of four hypomutable regions in (GCR1 (A, B, C, and D). Dispensable N-terminal (intronic) and C-terminal portions of the evolved region of GCR1 were included in the analysis as controls and were, as expected, not hypomutable. The analysis of several insertion, deletion, and point mutations, combined with a comparison of the hypomutability and hydrophobicity plots Gcr1p, suggested that some of the hypomutable regions may individually or in combination correspond to functionally important surface domains. In particular, we determined that region D contains a putative leucine zipper and is necessary and sufficient for Gcr1p homodimerization