Selective modulation of the functions of a conserved DNA motor by a histone fold complex

Abstract

Budding yeast Mph1 helicase and its orthologs drive multiple DNA transactions. Elucidating the mechanisms that regulate these motor proteins is central to understanding genome maintenance processes. Here, we show that the conserved histone fold MHF complex promotes Mph1-mediated repair of damaged replication forks but does not influence the outcome of DNA double-strand break repair. Mechanistically, scMHF relieves the inhibition imposed by the structural maintenance of chromosome protein Smc5 on Mph1 activities relevant to replication-associated repair through binding to Mph1 but not DNA. Thus, scMHF is a function-specific enhancer of Mph1 that enables flexible response to different genome repair situations.

Differential regulation of the anti-crossover and replication fork regression activities of Mph1 by Mte1

“…S1A). YOL086W-A encodes Mhf1, a component of the MHF complex that also harbors Mhf2 (Xue et al 2015a). YGR042W encodes a previously uncharacterized protein and was recently named Mte1 in the Saccharomyces Genome Database.…”

“…Several studies have provided insights into how FANCM, Mph1, and Fml1 execute their RF repair and anti-CO functions and how some of their activities are regulated to achieve the desired outcome (Schurer et al 2004;Gari et al 2008a,b;Sun et al 2008;Prakash et al 2009;Singh et al 2010;Yan et al 2010;Zheng et al 2011;Xue et al 2014Xue et al , 2015a. Results from biochemical and genetic studies have furnished evidence that these motor proteins convert stalled RFs into a "chicken foot" structure, which can be further processed to recruit the Rad51 recombinase to initiate HR (Xue et al 2015b).…”

“…In vivo studies have suggested that Mph1 is subject to negative regulation by Smc5-Smc6 so as to prevent the accumulation of toxic HR intermediates stemming from Mph1-mediated processing of damaged RFs (Chen et al 2009;Choi et al 2010;Chavez et al 2011;Xue et al 2014Xue et al , 2015b. Smc5/ 6 acts by preventing the assembly of Mph1 oligomers at the DNA junction of RF substrates, while MHF can overcome this inhibitory effect through competing with Smc5-Smc6 for Mph1 binding (Xue et al 2014(Xue et al , 2015a. Neither ScMHF nor Smc5/6 affects the anti-CO function of Mph1, suggesting that they are situation-specific regulators of the motor protein.…”

“…Corroborating these biochemical attributes, MHF functions with FANCM and Fml1 in RF repair in vivo (Singh et al 2010;Yan et al 2010;Bhattacharjee et al 2013). Interestingly, S. cerevisiae MHF (ScMHF) does not bind DNA or influence any of the known Mph1 enzymatic activities even though it physically interacts with the latter (Xue et al 2015a). However, ScMHF helps overcome the inhibitory effect of Smc5-Smc6 on RF regression and DNA branch migration in vitro (Xue et al 2015a).…”

“…Interestingly, S. cerevisiae MHF (ScMHF) does not bind DNA or influence any of the known Mph1 enzymatic activities even though it physically interacts with the latter (Xue et al 2015a). However, ScMHF helps overcome the inhibitory effect of Smc5-Smc6 on RF regression and DNA branch migration in vitro (Xue et al 2015a). In vivo studies have suggested that Mph1 is subject to negative regulation by Smc5-Smc6 so as to prevent the accumulation of toxic HR intermediates stemming from Mph1-mediated processing of damaged RFs (Chen et al 2009;Choi et al 2010;Chavez et al 2011;Xue et al 2014Xue et al , 2015b.…”