Helicase-related proteins

Tsukiyama, T., Becker, P.B., and Wu, C. (1994) ATP-dependent nucleosome disruption at a heat-shock promoter mediated by binding of GAGA transcription factor. Nature 367, 525-532. Laurent, B.C., Yang, X., and Carlson, M. (1992) An essential Saccharomyces cerevisiae gene homologous to SNF2 encodes a helicase-related protein in a new family. Mol. Cell Biol. 12, 1893-1902. 

Cells of patients with Bloom syndrome (BS) have many chromosome breaks and a high frequency of sister chromatid exchanges, perhaps in an effort to correct these breaks. The body is small but well-proportioned.kk A somewhat similar disease, the Werner syndrome (WS), is associated with premature aging.11 The Bloom s protein BLM and the WS gene product WRN are both helicases related to E.coli RecQ. Protein BLM colocalizes with replication protein A as discrete foci in the meiotic synaptonemal complex.1 3 Protein WRN also seems to be associated with DNA replication. Defects... 

Finally a number of gioups recendy came up with an intriguing new aspect of the link between PARP-1 and aging There are a few rare genedc disorders that induce premature aging in humans. One of these examples is Werner syndrome, due to mutation in the WPiNgput. The WRN gene encodes the WRN protein, a member of the RecQ helicase family which comprises an additional exonudease activity. WRN is part of the DNA replication complex and cooperates with several replication- and repair-relat proteins. Recendy, it was shown... 

An in-depth study of DNA repair systems (Aravind et al., 1999a) has concluded that few, if any, repair proteins occur with identical collinear domain arrangements in all three kingdoms of life. Approximately 10 enzyme families of adenosine triphosphatases (ATPases), photolyases, helicases, and nucleases were identified that are all likely to have been present in the cenancestor. These enzymatic domains are accompanied in DNA repair proteins by numerous regulatory domains. This indicates that the domain architectures of these proteins are labile, with incremental addition and/or subtraction of domains to conserved cores to be a common phenomenon except in the most closely related species. 

Both Rtel and dog-1 encode proteins which contain a conserved helicase motif as well as a domain for interaction with proliferating cell nuclear antigen (PCNA), part of the replication apparatus. This suggests that these proteins may function by unwinding G4 DNA that could otherwise impair replication. Biochemical analysis of the activities of RTEL, DOG-1, and related factors should prove very interesting. 

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