Sliding clamp

Insert the slide with the accession number, patient s name, into the slide clamps. 

Shamoo, Y. and Steitz, T. A. (1999). Building a replisome from interacting pieces sliding clamp complexed to a peptide from DNA polymerase and a polymerase editing complex. Cell 99,155-166. 

DNA polymerase III can polymerize DNA, but with a much lower processivity than one would expect for the organized replication of an entire chromosome. The necessary increase in processivity is provided by the addition of the J8 subunits, four of which complete the DNA polymerase III holoenzyme. The J3 subunits associate in pairs to form donut-shaped structures that encircle the DNA and act like clamps (Fig. 25-10b). Each dimer associates with a core subassembly of polymerase III (one dimeric clamp per core subassembly) and slides along the DNA as replication proceeds. The J8 sliding clamp prevents the dissociation of DNA polymerase III from DNA, dramatically increasing processivity—to greater than 500,000 (Table 25-1). 

Jeruzalmi, D., O DonneB, M., Kuriyan, J. (2002) Clamp loaders and sliding clamps. Curr. Opin. Struct. Biol. 12, 217-224. Summary of some of the elegant work elucidating how clamp loaders function. 

Kong, X-P, R. Onrust, M. O Donnell, and J. Kuriyan, Three-dimensional structure of the /3 subunit of E. coli DNA polymerase HI holoenzyme A sliding clamp. Cell 69 425-437, 1992. 

Clamp-loader (heteropentamer) 297.1 Assembles sliding-clamps, protein trafficking... 

Lopez de Saro FJ, Marinus MG, Modrich P, O Donnell M. The beta sliding clamp binds to multiple sites within MutL and MutS. J. Biol. Chem. 2006 281 14340-14349. 

Indian C, Mclnerney P, Georgescu R, Goodman ME, O Donnell M. A sliding-clamp toolbelt binds high- and low-fidelity DNA polymerases simultaneously. Mol. Cell 2005 19 805-815. Bunting KA, Roe SM, Pearl LH. Structural basis for recruitment of translesion DNA polymerase Pol JV/DinB to the beta-clamp. Embo. J. 2003 22 5883-5892. 

Thelen MP, Venclovas C, Eidelis K. A sliding clamp model... 

Majka J, Burgers PM. Yeast Radl7/Mec3/Ddcl a sliding clamp for the DNA damage checkpoint. Proc. Natl. Acad. Sci. U.S.A. 2003 100(5) 2249-2254. 

Figure 27.31. Structure of the Sliding Clamp. The dimeric P2 subunit of DNA polymerase III forms a ring that surrounds the DNA duplex. It allows the polymerase enzyme to move without falling off the DNA substrate. 

The polymerase holoenzyme assembles. The DNA polymerase ITT holoen-zyme assembles on the prepriming complex, initiated by interactions between DnaB and the sliding clamp subunit of DNA polymerase 111. These interactions also trigger ATP hydrolysis within the DnaA subunits, signaling the initiation of DNA replication. The breakup of the DnaA assembly prevents additional rounds of replication from beginning at the replication origin. 

The extreme level of BF inhibition is in contrast to steady-state analysis of human Pol 8. The degree of inhibition by 06-MeG observed for both the replicative Pol 8 (with the sliding clamp) and three recombinant Y-family polymerases (T, I, and k) was found to be relatively modest (10- to 100-fold) [149], With one exception, all of the human enzymes tested in the aforementioned study incorporated dCTP and dTTP equally well opposite 06-MeG. The exception to this pattern was human Pol t, which performed insertion of dTTP opposite 06-MeG 10 times better than dCTP opposite the lesion and with greater efficiency than dCTP opposite G (around 2-fold). It is entirely possible that inclusion of accessory proteins and/or post-translational modifications to the Y-family members could influence the catalytic efficiency of (/ -MeG bypass. In vitro studies with all polymerases studied to date verify the mutagenic potential of the 06-MeG adduct. 

Stukenberg P. T., Turner J., O Donnell M. (1994) An explanation for lagging strand replication Polymerase hopping among DNA sliding clamps. Cell 78 877. 

Venclovas, C., Thelen, M. P. (2000). Structure-based predictions of RADI, RAD9, HUSl and RAD17 participation in sliding clamp and clamp-loading complexes. Nucleic Acids Research, 28, 2481-2493. 

Sliding clamp - a protein dimer that encircles the DNA strand and helps hold the DNA polymerase to the DNA strand. 

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