Terminal, and telomere-associated proteins of pAL1, a linear plasmid from Arthrobacter nitroguajacolicus Rü61a

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Based on sequence analysis of the novel linear plasmid pAL1 of Arthrobacter nitroguajacolicus Rü61a, we propose that a subgroup of actinomycetal linear plasmids, represented by pBD2[1] and pAL1, have evolved a unique mechanism of telomere patching, involving an unprecedented telomere associated protein (Tap). The proteins of this telomere patching system may share some common motifs with the Tap and Tpg (terminal telomere binding) proteins of Streptomyces linear replicons, but appear to be significantly different, e.g., in their domain structure. The putative TappAL1 contains large additional domain(s) and may be distantly related to B-type DNA polymerases. The goal of this first project on an Arthrobacter linear plasmid is to identify all proteins bound to the termini and involved in telomere patching, and to characterize their function. We are especially interested in investigating the role of the presumptive TappAL1 in interacting with the DNA and/or the terminal protein(s) (TpgpAL1), and its potential catalytic activity in telomere patching. The main objectives are: Identification of the Tpg protein(s); identification of (further) proteins with specific affinity to the telomeres; expression cloning of tpgpAL1 and tappAL1; functional studies (i) addressing the specificity of DNA binding of TpgpAL1, TappAL1 (and/or other proteins), (ii) assessing the interaction of TpgpAL1 and TappAL1, and (iii) analysing whether TappAL1 shows desoxynucleotidylation (primase, polymerase) activity. The ultimate goal is to understand the mechanism of telomere patching. [1] Stecker C, Johann A, Herzberg C, Averhoff B, Gottschalk G (2003) J Bacteriol 185: 5269-5274.