A telomerase-associated RecQ protein-like helicase resolves telomeric G-quadruplex structures during replication

• Published in: Gene 2012-04, Vol.497 (2), p.147-154
• Main Authors: Postberg, Jan, Tsytlonok, Maksym, Sparvoli, Daniela, Rhodes, Daniela, Lipps, Hans J.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; cell cycle; Ciliates; DNA; DNA Helicases - genetics; DNA Helicases - metabolism; DNA Replication - genetics; DNA Replication - physiology; Escherichia coli; eukaryotic cells; G-Quadruplexes; Genome; humans; Immunoprecipitation - methods; in vitro studies; Macronucleus; Macronucleus - genetics; Molecular Sequence Data; phosphorylation; proteins; RecQ Helicases - genetics; RecQ Helicases - metabolism; Replication band; RNA interference; S Phase - genetics; Sporadotrichina - genetics; Sporadotrichina - metabolism; Stylonychia lemnae; telomerase; Telomerase - genetics; Telomerase - metabolism; Telomere - genetics; Telomere - metabolism; Telomere-Binding Proteins - genetics; Telomere-Binding Proteins - metabolism; telomeres; Tert
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2012.01.068

It is well established that G-quadruplex DNA structures form at ciliate telomeres and their formation throughout the cell-cycle by telomere-end-binding proteins (TEBPs) has been analyzed. During replication telomeric G-quadruplex structure has to be resolved to allow telomere replication by telomerase. It was shown that both phosphorylation of TEBPβ and binding of telomerase are prerequisites for this process, but probably not sufficient to unfold G-quadruplex structure in timely manner to allow replication to proceed. Here we describe a RecQ-like helicase required for unfolding of G-quadruplex structures in vivo. This helicase is highly reminiscent of human RecQ protein-like 4 helicase as well as other RecQ-like helicase found in various eukaryotes and E. coli. In situ analyses combined with specific silencing of either the telomerase or the helicase by RNAi and co-immunoprecipitation experiments demonstrate that this helicase is associated with telomerase during replication and becomes recruited to telomeres by this enzyme. In vitro assays showed that a nuclear extract prepared from cells in S-phase containing both the telomerase as well as the helicase resolves telomeric G-quadruplex structure. This finding can be incorporated into a mechanistic model about the replication of telomeric G-quadruplex structures during the cell cycle. ► Stylonychia StyRecQL is a helicase reminiscent of human RecQ protein-like 4. ► StyRecQL is enriched in replication band of the macronucleus during S-phase. ► StyRecQL colocalizes and is associated with Tert during telomere replication.