Sgs1 truncations induce genome rearrangements but suppress detrimental effects of BLM overexpression in Saccharomyces cerevisiae.
RecQ-like DNA helicases are conserved from bacteria to humans. They perform functions in the maintenance of genome stability, and their mutation is associated with cancer predisposition and premature aging syndromes in humans. Here, a series of C-terminal deletions and point mutations of Sgs1, the only RecQ-like helicase in yeast, show that the Helicase/RNase D C-terminal domain and the Rad51 interaction domain are dispensable for Sgs1's role in suppressing genome instability, whereas the zinc-binding domain and the helicase domain are required. BLM expression from the native SGS1 promoter had no adverse effects on cell growth and was unable to complement any sgs1Δ defects. BLM overexpression, however, significantly increased the rate of accumulating gross-chromosomal rearrangements in a dosage-dependent manner and greatly exacerbated sensitivity to DNA-damaging agents. Co-expressing sgs1 truncations of up to 900 residues, lacking all known functional domains of Sgs1, suppressed the hydroxyurea sensitivity of BLM-overexpressing cells, suggesting a functional relationship between Sgs1 and BLM. Protein disorder prediction analysis of Sgs1 and BLM was used to produce a functional Sgs1-BLM chimera by replacing the N-terminus of BLM with the disordered N-terminus of Sgs1. The functionality of this chimera suggests that it is the disordered N-terminus, a site of protein binding and posttranslational modification, that confers species specificity to these two RecQ-like proteins.
Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620, USA.
Hamed
H
Mirzaei
Salahuddin
S
Syed
Jessica
J
Kennedy
Kristina H
KH
Schmidt
D000595:Amino Acid Sequence; D001816:Bloom Syndrome / Q000201:enzymology / Q000235:genetics; D015870:Gene Expression; D015321:Gene Rearrangement; D005800:Genes, Fungal; D042822:Genomic Instability; D006801:Humans; D008969:Molecular Sequence Data; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D054730:Protein Interaction Domains and Motifs; D053484:RecQ Helicases / Q000737:chemistry / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C097151:Bloom syndrome protein; C090472:SGS1 protein, S cerevisiae; D053484:RecQ Helicases