hMSH4-hMSH5 recognizes Holliday Junctions and forms a meiosis-specific sliding clamp that embraces homologous chromosomes.
Five MutS homologs (MSH), which form three heterodimeric protein complexes, have been identified in eukaryotes. While the human hMSH2-hMSH3 and hMSH2-hMSH6 heterodimers operate primarily in mitotic mismatch repair (MMR), the biochemical function(s) of the meiosis-specific hMSH4-hMSH5 heterodimer is unknown. Here, we demonstrate that purified hMSH4-hMSH5 binds uniquely to Holliday Junctions. Holliday Junctions stimulate the hMSH4-hMSH5 ATP hydrolysis (ATPase) activity, which is controlled by Holliday Junction-provoked ADP-->ATP exchange. ATP binding by hMSH4-hMSH5 induces the formation of a hydrolysis-independent sliding clamp that dissociates from the Holliday Junction crossover region, embracing two homologous duplex DNA arms. Fundamental differences between hMSH2-hMSH6 and hMSH4-hMSH5 Holliday Junction recognition are detailed. Our results support the attractive possibility that hMSH4-hMSH5 stabilizes and preserves a meiotic bimolecular double-strand break repair (DSBR) intermediate.
Genetics and Molecular Biology Program, Kimmel Cancer Center, BLSB 933, 233 South 10th Street, Philadelphia, PA 19107, USA.
Timothy
T
Snowden
Samir
S
Acharya
Charles
C
Butz
Mark
M
Berardini
Richard
R
Fishel
D000251:Adenosine Triphosphatases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002877:Chromosomes, Human / Q000378:metabolism*; D045566:DNA, Cruciform / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D008540:Meiosis / Q000502:physiology*; D011506:Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D018797:Cell Cycle Proteins; D045566:DNA, Cruciform; C409221:MSH4 protein, human; C118481:MSH5 protein, human; D011506:Proteins; D000251:Adenosine Triphosphatases