Effect of the multifunctional proteins RPA, YB-1, and XPC repair factor on AP site cleavage by DNA glycosylase NEIL1
Abstract
DNA glycosylases are key enzymes in thefirst step of base excision DNA repair, recognizing DNA damage and catalyzingthe release of damaged nucleobases. Bifunctional DNA glycosylases also possess associated apurinic/apyrimidinic (AP)lyase activity that nick the damaged DNA strand at an abasic (or AP) site, formed either spontaneously or at thefirst stepof repair. NEIL1 is a bifunctional DNA glycosylase capable of processing lesions, including AP sites, not only in double-stranded but also in single-stranded DNA. Here, we show that proteins participating in DNA damage response, YB-1 andRPA, affect AP site cleavage by NEIL1. Stimulation of the AP lyase activity of NEIL1 was observed when an AP site waslocated in a 60nt-long double-stranded DNA. Both RPA and YB-1 inhibited AP site cleavage by NEIL1 when the AP sitewas located in single-stranded DNA. Taking into account a direct interaction of YB-1 with the AP site, located in single-stranded DNA, and the high affinity of both YB-1 and RPA for single-stranded DNA, this behavior is presumably aconsequence of a competition with NEIL1 for the DNA substrate. Xeroderma pigmentosum complementation groupC protein (XPC), a key protein of another DNA repair pathway, was shown to interact directly with AP sites but hadno effect on AP site cleavage by NEIL1.