DNA复制-第五讲.ppt

免疫学信息网HTTP://WWW.IMMUNEWEB.COM Formation of pre-Replicative complex 免疫学信息网HTTP://WWW.IMMUNEWEB.COM REPLICATION COMPLEXES DURING THE CELL CYCLE 免疫学信息网HTTP://WWW.IMMUNEWEB.COM G2 M ORC MCM MCM CDC6 + Cdt1 Replication Machinery “Pre-Replicative Complex” ORC CDC6+ Cdt1 S late G1 early G1 免疫学信息网HTTP://WWW.IMMUNEWEB.COM Eukaryotic initiation complex ORC : A six subunit protein complex which has been implicated as being the eukaryotic DNA replication initiator protein. Subunits are named according to their size, with ORC1 being the largest and ORC6 being the smallest subunit. Yeast ORC specifically binds to replication origins in an ATP dependent manner and has been shown to possess ATPase activity.? CDC6/Cdc18 : An essential factor for the assembly of the pre-replicative complexes that co-operates with Cdt1 to load MCM2-7 Proteolyzed in yeasts or exported out of the nucleus in mammalian cells at the G1- S transition. Overexpression of Cdc6 in yeast causes multiple rounds of DNA replication without intervening mitosis, making it a critical regulator of DNA replication.? MCM2-7 : A family of six related proteins (MCM2-MCM7) which seem to function together in a large multi-subunit protein complex. The role of MCMís in DNA replication is still speculative, ranging from mediation of protein-DNA interactions to DNA helicase activity.? 免疫学信息网HTTP://WWW.IMMUNEWEB.COM A/T DUE ORE Auxiliary elements Auxiliary elements Origin recognition proteins Transcription Factors Transcription Factors Leading str Leading str Lagging str Lagging str Core origin Origins are multi-partite THE STRUCTURE OF ARS1(S. CEREVISIAE) 免疫学信息网HTTP://WWW.IMMUNEWEB.COM B 1 ACS B 2 B 3 ABF1 ORC “Post-RC” protection “Pre-RC” protection 1 3 4 5 6 4 1 2 2 免疫学信息网HTTP://WWW.IMMUNEWEB.COM 免疫学信息网HTTP://WWW.IMMUNEWEB.COM ORC uses different strategies for binding DNA in different species 免疫学信息网HTTP://WWW.IMMUNEWEB.COM Pre-RC formation ORC : A six subunit protein complex which has been implicated as being the