Pleiotropic roles for mycobacterial DinB2 in frameshift and substitution mutagenesis

Abstract

Translesion synthesis mediated by translesion polymerases is a conserved mechanism of DNA damage tolerance. In bacteria, DinB enzymes are widely distributed promutagenic translesion polymerases. The role of DinBs in mycobacterial mutagenesis was unclear until recent studies revealed a role for mycobacterial DinB1 in substitution and frameshift mutagenesis, overlapping with that of translesion polymerase DnaE2. M. smegmatis encodes two additional DinBs (DinB2 and DinB3) and M. tuberculosis encodes DinB2, but the roles of these polymerases in mycobacterial damage tolerance and mutagenesis is unknown. The biochemical properties of DinB2, including facile utilization of ribonucleotides and 8-oxo-guanine, suggest that DinB2 could be a promutagenic polymerase. Here we examine the effects of DinB2 and DinB3 overexpression in mycobacterial cells. We demonstrate that DinB2 can drive diverse substitution mutations conferring antibiotic resistance. DinB2 induces frameshift mutations in homopolymeric sequences, both in vitro and in vivo. DinB2 switches from less to more mutagenic in the presence of manganese in vitro. This study indicates that DinB2 may contribute to mycobacterial mutagenesis and antibiotic resistance acquisition in combination with DinB1 and DnaE2.

A nucleoid-associated protein is involved in the emergence of antibiotic resistance by promoting the frequent exchange of the replicative DNA polymerase inM. smegmatis

“…In mycobacteria, the fidelity of chromosome replication is established by the major replicative polymerase DnaE1, which possesses endogenous proofreading activity (4). In addition to DnaE1, mycobacteria encode a suite of other polymerases with specialized repair functions that are only expressed under certain conditions, such as oxidative or DNA-damaging stress (5)(6)(7). For example, the mycobacterial specialist polymerases DinB1, DinB2, DinB3, and DnaE2 are induced under different conditions and have varying repair activities and mutational signatures (5)(6)(7)(8)(9)(10).…”

“…In addition to DnaE1, mycobacteria encode a suite of other polymerases with specialized repair functions that are only expressed under certain conditions, such as oxidative or DNA-damaging stress (5)(6)(7). For example, the mycobacterial specialist polymerases DinB1, DinB2, DinB3, and DnaE2 are induced under different conditions and have varying repair activities and mutational signatures (5)(6)(7)(8)(9)(10). Of particular importance is the error-prone polymerase DnaE2.…”