This entry represents the SOS response associated peptidase (SRAP) superfamily.The SRAP (SOS-response associated peptidase) family is characterised by the SRAP domain with a novel thiol autopeptidase activity, whose active site in human HMCES is comprised of the catalytic triad residues C2, E127, and H210 []. SRAP proteins are evolutionarily conserved in all domains of life. For instance, human HMCES and E. coli YedK are similar in both sequence and structure []. HMCES was originally identified as a possible reader of 5hmC in embryonic stem cell extracts using a double-stranded DNA molecule containing 5hmC as bait []. The bacterial members have operonic associations with the SOS DNA damage response, mutagenic translesion DNA polymerases, non-homologous DNA-ending-joining networks that employ Ku and an ATP-dependent ligase, and other repair systems []. Abasic (AP) sites are one of the most common DNA lesions that block replicative polymerases. SRAP proteins shield the AP site from endonucleases and error-prone polymerases []. Both HMCES and YedK have been found to preferentially bind ssDNA and efficiently form DNA-protein crosslinks (DPCs) to AP sites in ssDNA. They crosslink to AP sites via a stable thiazolidine DNA-protein linkage formed with the N-erminal cysteine and the aldehyde form of the AP deoxyribose []. In B Cells, HMCES has also been shown to mediate microhomology-mediated alternative-end-joining through its SRAP domain [].
The SRAP (SOS-response associated peptidase) family is characterised by the SRAP domain with a novel thiol autopeptidase activity, whose active site in human HMCES is comprised of the catalytic triad residues C2, E127, and H210 []. SRAP proteins are evolutionarily conserved in all domains of life. For instance, human HMCES and E. coli YedK are similar in both sequence and structure []. HMCES was originally identified as a possible reader of 5hmC in embryonic stem cell extracts using a double-stranded DNA molecule containing 5hmC as bait []. The bacterial members have operonic associations with the SOS DNA damage response, mutagenic translesion DNA polymerases, non-homologous DNA-ending-joining networks that employ Ku and an ATP-dependent ligase, and other repair systems []. Abasic (AP) sites are one of the most common DNA lesions that block replicative polymerases. SRAP proteins shield the AP site from endonucleases and error-prone polymerases []. Both HMCES and YedK have been found to preferentially bind ssDNA and efficiently form DNA-protein crosslinks (DPCs) to AP sites in ssDNA. They crosslink to AP sites via a stable thiazolidine DNA-protein linkage formed with the N-erminal cysteine and the aldehyde form of the AP deoxyribose []. In B Cells, HMCES has also been shown to mediate microhomology-mediated alternative-end-joining through its SRAP domain [].
