Poster abstracts
Poster number 17 submitted by Jagat Budhathoki
Implications of Weak GQ Unfolding Activity of RecQL5 Helicase
Jagat B. Budhathoki (Department Of Physics, Kent State University), Hamza Balci (Department Of Physics, Kent State University), Parastoo Maleki (Department Of Physics, Kent State University), William Roy (Department Of Physics, Kent State University), Jaya G. Yodh (Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign), Pavel Janscak (Institute of Molecular Cancer Research, University of Zurich)
Abstract:
RecQL5 is a homologue of E.Coli RecQ helicase and is one of five members of RecQ family of helicases in humans. Even though some other members of this family are associated with different syndromes, such as Bloom (BLM) and Werner (WRN) syndromes which result from deficiencies in respective helicases, RecQL5 has not been directly linked with a specific syndrome. Both Werner and Bloom helicases are considered to be involved in resolving non-canonical DNA structures, such as G-quadruplex (GQ). Deficiencies in this activity are known to result in DNA breaks and genomic instability. Whether RecQL5, which is not directly associated with a syndrome, also possesses GQ unfolding activity is an important question that could provide further insight onto the significance of GQ structures in the syndromes associated with RecQ family of helicases. In our earlier work, we showed that BLM helicase unfolds GQs with and without ATP, which we attributed the latter to be due to binding of BLM to the vicinity of GQ and interacting with it. Our single molecule FRET studies show that the RecQL5 lacks GQ unfolding activity in the absence of ATP for the same DNA substrates used in the BLM study under physiological salt and pH conditions. However, RecQL5- mediated GQ unfolding takes place in the presence of ATP although, at a significantly lower efficiency compared to BLM. Our studies of this activity under different salt conditions and for different GQ constructs demonstrated a strong dependence on GQ stability. Therefore, we conclude that RecQL5 is a less efficient GQ destabilizer but may assist the more efficient helicases, such as BLM and WRN, in this task. Overall, these results are consistent with GQs being significant components of Bloom and Werner syndromes, and might explain why deficiencies in RecQL5 are not directly associated with a similar syndrome.
Keywords: G Quadruplex, RecQ helicase, Unfolding