Non-hexameric DNA helicases and translocases: mechanisms and regulation

Abstract

Helicases and nucleic acid translocases are motor proteins that have essential roles in nearly all aspects of nucleic acid metabolism, ranging from DNA replication to chromatin remodelling. Fuelled by the binding and hydrolysis of nucleoside triphosphates, helicases move along nucleic acid filaments and separate double-stranded DNA into their complementary single strands. Recent evidence indicates that the ability to simply translocate along single-stranded DNA is, in many cases, insufficient for helicase activity. For some of these enzymes, self assembly and/or interactions with accessory proteins seem to regulate their translocase and helicase activities.

RecQ helicases: Multiple structures for multiple functions?

“…These motifs are required for the enzyme to bind NTP and couple the energy derived from NTP hydrolysis to the process of nucleic acid unwinding (Lohman et al, 2008;Matson et al, 1994;Singleton and Wigley, 2002;von Hippel, 2004). The determination of crystal structures of various helicases of the SF1 and SF2 family has shown that these motifs form the core of two RecA-like domains that serve as the ATPdriven "motor" of the helicase.…”

“…Helicases are a seemingly ever expanding family of enzymes that catalyze DNA strand separation in a reaction coupled to the binding and hydrolysis of nucleotide triphosphate (NTP) (Matson et al, 1994;Singleton and Wigley, 2002;von Hippel, 2004). A detailed description of the different superfamilies of helicases and their properties is outside the scope of this article, and we refer readers to recent reviews (Lohman et al, 2008;Singleton et al, 2007;von Hippel, 2004). RecQ enzymes are a subfamily of helicases that play an essential role in the maintenance of genome stability by acting at the interface between DNA replication, recombination, and repair Bohr, 2008;Hickson, 2003).…”

Yeast Helicase Pif1 Unwinds RNA:DNA Hybrids with Higher Processivity than DNA:DNA Duplexes

“…They participate in many different cellular events, ranging from DNA replication to chromatin remodeling (2). Many helicases contain two conserved RecA-like helicase domains with an ATP-binding site at the interface of the core domains (3).…”

Roles of DEAD-box proteins in RNA and RNP Folding

“…2). First, whereas conventional helicases unwind helices by translocating along one of the strands and typically have processivity measured in the range of hundreds to thousands of base pairs, 39,40 DEAD-box proteins have very low processivity, displaying little or no unwinding of helices longer than about 25-40 base pairs. [41][42][43] Increased duplex stability, Figure 1.…”

“…2A). 39,40 In contrast, some DEAD-box proteins can unwind blunt-ended helices just as efficiently as those with extensions, 44,53,54 again suggesting the unwinding is initiated by a direct interaction with a duplex, and although other DEAD-box proteins are activated by extensions, there is no requirement for a defined polarity (reviewed in refs. 17 and 48).…”