Two X family DNA polymerases, λ and μ, in meiotic tissues of the basidiomycete, Coprinus cinereus

Abstract

The X family DNA polymerases lambda (CcPollambda) and mu (CcPolmu) were shown to be expressed during meiotic prophase in the basidiomycete, Coprinus cinereus. These two polymerases are the only members of the X family in the C. cinereus genome. The open reading frame of CcPollambda encoded a predicted product of 800 amino acid residues and that of CcPolmicro of 621 amino acid residues. Both CcPollambda and CcPolmicro required Mn(2+) ions for activity, and both were strongly inhibited by dideoxythymidine triphosphate. Unlike their mammalian counterparts, CcPollambda and CcPolmicro had no terminal deoxynucleotidyl transferase activity. Immunostaining analysis revealed that CcPollambda was present at meiotic prophase nuclei in zygotene and pachytene cells, which is the period when homologous chromosomes pair and recombine. CcPolmicro was present in a slightly wider range of cell stages, zygotene to diplotene. In analyses using D-loop recombination intermediate substrates, we found that both CcPollambda and CcPolmicro could promote primer extension of an invading strand in a D-loop structure. Moreover, both polymerases could fully extend the primer in the D-loop substrate, suggesting that D-loop extension is an activity intrinsic to CcPollambda and CcPolmicro. Based on these data, we discuss the possible roles of these polymerases in meiosis.

Elevated Mutagenicity in Meiosis and Its Mechanism

“…Polymerase lambda (Polλ) shows partial sequence identity to Polβ and is expressed during meiosis in some fungi and mammals . S. cerevisiae Pol4 shows sequence similarity to Polλ at the N‐terminal domain .…”

Eukaryotic DNA Polymerases in Homologous Recombination

“…The human Pol λ allele, R438W , revealed a defect in sister chromatid exchange and sensitivity to the topoisomerase inhibitor camptothecin. This led authors to infer a function of Pol λ in HR (14), which had also been inferred from its induced expression during meiosis in fungi and mammals (29, 125, 135). The S. cerevisiae pol4 mutant reveals a meiotic hyper-recombination phenotype, which could be the result of an HR role of Pol λ, but the genetic analysis remains incomplete (68).…”

Coprinus cinereus Mer3 is required for synaptonemal complex formation during meiosis

“…Not only is its meiotic cell cycle long and naturally synchronous, but large populations of synchronous meiotic cells are also easy to obtain (Li et al 1999;Kües 2000;Kamada 2002;Casselton and Olesnicky 1998). These advantages have enabled us to isolate and characterize many synapsis-related proteins in C. cinereus (Nara et al 1999(Nara et al , 2001Hamada et al 2007;Ishizaki et al 2002;Namekawa et al 2003a, b, c;Yamaguchi et al 2004;Iwabata et al 2005;Koshiyama et al 2006;Sakamoto et al 2007;Sakaguchi et al 2007) and to demonstrate their roles in vivo.…”