Specialized Helicases Maintain G-Rich Genomic Regions

1 Specialized Helicases Maintain G-Rich Genomic Regions 

The RecQ helicases comprise a small, conserved enzyme family which is essential for maintenance of genomic stability in organisms from E. coli to human. There is only one RecQ family member in E. coli (RecQ), one in S. cerevisiae (Sgsl), one in S. pombe (Rqhl), and five in Homo sapiens. Three human members of the RecQ family are associated with genomic instability and predisposition to malignancies WRN with Werner s syndrome, BLM with Bloom s syndrome, and RTS (or RECQ4) with Rothmund-Thompson syndrome. RecQ helicases are unusual in their ability to unwind G4 DNA,  

1 Nucleolar Functions of RecQ Family Members Eukaryotic ribosomal RNA (rRNA) is transcribed from a family of repeated DNA sequences, ribosomal DNA, rDNA. rDNA repeats are G-rich on the non-template strand, not only within the regions that encode ribosomal RNA but also in the spacer regions. rDNA transcription and rRNA biogenesis occur 

2 WRN Helicase Unwinds G4 DNA to Promote Mitotic Replication of Telomeres 

The possibility that the human RecQ helicase, WRN, may function to maintain telomeres has drawn considerable attention because premature aging is the hallmark of Werner syndrome. Afiected individuals develop normally until their teens, then rapidly develop characteristics of aging, including graying hair, alopecia, osteoporosis, type II diabetes and cataracts, and premature death, at an average age of 40. This is accompanied by chromosomal instability and cancer. 

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