Protein
Crossover junction endonuclease MUS81
Organism
Saccharomyces cerevisiae (strain ATCC 204508 / S288c)
Function
Interacts with MMS4 to form a DNA structure-specific endonuclease with substrate preference for branched DNA structures with a 5'-end at the branch nick. Typical substrates include 3'-flap structures, D-loops, replication forks with regressed leading strands and nicked Holliday junctions. Cleavage probably occurs approximately half a helical turn upstream of the free 5'-end in these structures. May be required in mitosis for the processing of stalled replication fork intermediates arising spontaneously or subsequent to treatment with DNA damaging agents such as methylmethane sulfonate (MMS), camptothecin (CPT) or UV. May be required in meiosis for the repair of meiosis-specific double strand breaks subsequent to single-end invasion (SEI). This involves consecutive cleavage of D-loops and nicked Holliday junctions leading to sister chromatid crossover. In contrast to MSH4-MSH5 dependent crossover, double Holliday junctions do not seem to be involved. Spore formation and viability are severely impaired in deletion strains.
Similarity
Belongs to the XPF family.
Sequence
MELSSNLKDLYIEWLQELVDGLTPKQEQLKIAYEKAKRNLQNAEGSFYYPTDLKKVKGIGNTIIKRLDTKLRNYCKIHHISPVEAPSLTQTSSTRPPKRTTTALRSIVNSCENDKNEAPEEKGTKKRKTRKYIPKKRSGGYAILLSLLELNAIPRGVSKEQIIEVAGKYSDHCMTPNFSTKEFYGAWSSIAALKKHSLVLEEGRPKRYSLTEEGVELTKSLKTADGISFPKENEEPNEYSVTRNESSEFTANLTDLRGEYGKEEEPCDINNTSFMLDITFQDLSTPQRLQNNVFKNDRLNSQTNISSHKLEEVSDDQTVPDSALKAKSTIKRRRYNGVSYELWCSGDFEVFPIIDHREIKSQSDREFFSRAFERKGMKSEIRQLALGDIIWVAKNKNTGLQCVLNTIVERKRLDDLALSIRDNRFMEQKNRLEKSGCEHKYYLIEETMSGNIGNMNEALKTALWVILVYYKFSMIRTCNSDETVEKIHALHTVISHHYSQKDLIVIFPSDLKSKDDYKKVLLQFRREFERKGGIECCHNLECFQELMGKGDLKTVGELTIHVLMLVKGISLEKAVAIQEIFPTLNKILMAYKTCSSEEEAKLLMFNVLGDAPGAKKITKSLSEKIYDAFGKL