Inter-Species DNA Polymerase delta Chimeras are Functional in Saccharomyces Cerevisiae

Detection of two loci involved in (1-->3)-beta-glucan (curdlan) biosynthesis by Agrobacterium sp. ATCC31749, and comparative sequence analysis of the putative curdlan synthase gene

Genes essential for the production of a linear, bacterial (1-->3)-beta-glucan, curdlan, have been cloned for the first time from Agrobacterium sp. ATCC31749. The genes occurred in two, nonoverlapping, genomic fragments that complemented different sets of curdlan( crd )-deficient transposon-insertion mutations. These were detected as colonies that failed to stain with aniline blue, a (1-->3)-beta-glucan specific dye. One fragment carried a biosynthetic gene cluster (locus I) containing the putative curdlan synthase gene, crdS, and at least two other crd genes. The second fragment may contain only a single crd gene (locus II). Determination of the DNA sequence adjacent to several locus I mutations revealed homology to known sequences only in the cases of crdS mutations. Complete sequencing of the 1623 bp crdS gene revealed highest similarities between the predicted CrdS protein (540 amino acids) and glycosyl transferases with repetitive action patterns. These include bacterial cellulose synthases (and their homologs), which form (1-->4)-beta-glucans. No similarity was detected with putative (1-->3)-beta-glucan synthases from yeasts and filamentous fungi. Whatever the determinants of the linkage specificity of these beta-glucan synthases might be, these results raise the possibility that (1-->3)-beta-glucans and (1-->4)-beta-glucans are formed by related catalytic polypeptides.

Cloning, chromosomal localization, and interspecies interaction of mouse DNA polymerase delta small subunit (PolD2)

DNA polymerase delta core is a heterodimeric enzyme with a catalytic subunit of 125 kDa and a second subunit of 50 kDa with an as yet unknown function. It is an essential enzyme for DNA replication and DNA repair. We cloned the full-length cDNA encoding the DNA polymerase delta small subunit from mouse cells. The sequence of the predicted polypeptide of 51,336 Da is, like the catalytic subunit, highly conserved not only among mammals (93% identity and 96% similarity), but also between yeast and mammals (34% identity and 57% similarity). Fluorescence in situ hybridization experiments indicated that the gene for the small DNA polymerase delta of mouse is localized on chromosome 11, band A2. By using the yeast two-hybrid system we found that the mouse 125-kDa DNA polymerase catalytic subunit is able to interact with the 50-kDa subunit of the human enzyme, suggesting an in vivo interspecies interaction between the two subunits of DNA polymerase delta.