RecQ helicase

RecQ helicase is a family of helicase enzymes initially found in Escherichia coli that has been shown to be important in genome maintenance. They function through catalyzing the reaction ATP + H₂O → ADP + P and thus driving the unwinding of paired DNA and translocating in the 3' to 5' direction. These enzymes can also drive the reaction NTP + H₂O → NDP + P to drive the unwinding of either DNA or RNA.

Function

In prokaryotes RecQ is necessary for plasmid recombination and DNA repair from UV-light, free radicals, and alkylating agents. This protein can also reverse damage from replication errors. In eukaryotes, replication does not proceed normally in the absence of RecQ proteins, which also function in aging, silencing, recombination and DNA repair.

Structure

RecQ family members share three regions of conserved protein sequence referred to as the:

The removal of the N-terminal residues (Helicase and, RecQ-Ct domains) impairs both helicase and ATPase activity but has no effect on the binding ability of RecQ implying that the N-terminus functions as the catalytic end. Truncations of the C-terminus (HRDC domain) compromise the binding ability of RecQ but not the catalytic function. The importance of RecQ in cellular functions is exemplified by human diseases, which all lead to genomic instability and a predisposition to cancer.

Werner syndrome ATP-dependent helicase

Werner syndrome ATP-dependent helicase also known as DNA helicase, RecQ-like type 3 is an enzyme that in humans is encoded by the WRN gene. WRN is a member of the RecQ Helicase family. Helicase enzymes generally unwind and separate double-stranded DNA. These activities are necessary before DNA can be copied in preparation for cell division (DNA replication). Helicase enzymes are also critical for making a blueprint of a gene for protein production, a process called transcription. Further evidence suggests that Werner protein plays a critical role in repairing DNA. Overall, this protein helps maintain the structure and integrity of a person's DNA.

The WRN gene is located on the short (p) arm of chromosome 8 between positions 12 and 11.2, from base pair 31,010,319 to base pair 31,150,818.

Structure and function

WRN is a member of the RecQ Helicase family. It is the only RecQ Helicase that contains 3' to 5' exonuclease activity. These exonuclease activities include degradation of recessed 3' ends and initiation of DNA degradation from a gap in dsDNA. WRN is important in reparation of double stranded breaks, nonhomologous end joining, and base excision repair. WRN may also be important in telomere maintenance and replication, especially the replication of the G-rich sequences.