DescriptionBeetle1 is a LTR retrotransposon characterized in Beta vulgaris (Weber and Schmidt 2003). Beetle1 belongs to the Chromoviridae branch, term suggested (Marín and Lloréns 2000) to describe the Ty3/Gypsy elements bearing chromodomain-integrases (Malik and Eickbush 1999). The chromovirus branch is probably the most ancient phylogenetic pattern of Ty3/Gypsy retroelements (Gorinsek, Gubensek and Kordis 2004; 2005; Kordis 2005). Within chromoviruses, Beetle1 belongs to CRM clade, a centromere-associated sub-lineage characterized by encoding integrases, which are clearly divergent from that encoded by other lineages of chromoviruses (Gorinsek, Gubensek, and Kordis 2004). The genomic structure of of this element is 6.7 Kb in size, including LTRs of 546 nt. The internal region displays a Primer Binding Site (PBS), a single Open Reading Frame (ORF) coding for a gag-pol precursor, and a Polypurine Tract (PPT) adjacent to the 3´LTR (Weber and Schmidt 2003). The PBS of fungi and vertebrate chromoviruses, differs significantly from that used by plant chromoviruses. While plant chromoviruses use a methionine starting tRNA (iMet), fungi and vertebrate chromoviruses use their own self-priming mechanism to start the reverse transcription (Levin 1995 ; Butler et al. 2001). Structure
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Llorens, C., Futami, R., Covelli, L., Dominguez-Escriba, L., Viu, J.M., Tamarit, D., Aguilar-Rodriguez, J. Vicente-Ripolles, M., Fuster, G., Bernet, G.P., Maumus, F., Munoz-Pomer, A., Sempere, J.M., LaTorre, A., Moya, A. (2011) The Gypsy Database (GyDB) of Mobile Genetic Elements: Release 2.0 Nucleic Acids Research (NARESE) 39 (suppl 1): D70-D74 doi: 10.1093/nar/gkq1061