Translesion DNA synthesis (TLS) by specialized DNA polymerases (Pols) is a conserved mechanism for tolerating replication blocking DNA lesions. The actions of TLS Pols are managed in part by ring-shaped sliding clamp proteins. In addition to catalyzing TLS, altered expression of TLS Pols impedes cellular growth. The goal of this study was to define the relationship between the physiological fun...

In addition to RNA polymerases I, II, and III, the essential RNA polymerases present in all eukaryotes, plants have two additional nuclear RNA polymerases, abbreviated as Pol IV and Pol V, that play nonredundant roles in siRNA-directed DNA methylation and gene silencing. We show that Arabidopsis Pol IV and Pol V are composed of subunits that are paralogous or identical to the 12 subunits of Pol...

Mammalian DNA polymerase (pol) is a member of the X-family of DNA polymerases and has striking enzymatic and structural similarities to mammalian DNA pol . Because pol provides two important enzymatic activities for base excision repair (BER), we examined whether pol might also contribute to BER. We used extracts from mouse embryonic fibroblasts representing wild-type and null genotypes for pol...

A new form of DNA polymerase III, termed Pol III star (Pol III(*)), has been purified to homogeneity from Escherichia coli. Pol III(*) is temperature sensitive when isolated from a thermo-sensitive dnaE mutant, as had been described for Pol III. Pol III(*) and Pol III are separable by gel filtration. Pol III(*) utilizes a duplex template containing short gaps with the same catalytic properties ...

Proliferating cell nuclear antigen (PCNA) has been shown to interact with a variety of DNA polymerases (pol) such as pol delta, pol epsilon, pol iota, pol kappa, pol eta, and pol beta. Here we show that PCNA directly interacts with the newly discovered pol lambda cloned from human cells. This interaction stabilizes the binding of pol lambda to the primer template, thus increasing its affinity f...

Nuclear multisubunit RNA polymerases IV and V (Pol IV and Pol V) evolved in plants as specialized forms of Pol II. Their functions are best understood in the context of RNA-directed DNA methylation (RdDM), a process in which Pol IV-dependent 24 nt siRNAs direct the de novo cytosine methylation of regions transcribed by Pol V. Pol V has additional functions, independent of Pol IV and 24 nt siRNA...

The dnaN159 allele encodes a temperature-sensitive mutant form of the β sliding clamp (β159). SOS-induced levels of DNA polymerase IV (Pol IV) confer UV sensitivity upon the dnaN159 strain, while levels of Pol IV ∼4-fold higher than those induced by the SOS response severely impede its growth. Here, we used mutations in Pol IV that disrupted specific interactions with the β clamp to test our hy...