[Endogenous cellular reverse transcriptase in the rat brain. A comparative analysis of the authentic enzyme and...

A purified preparation of endogenous RNA-dependent DNA-polymerase (reverse transcriptase) earlier identified in rat brain (Ivanov, V.A., Pakhotin, P.I., Bobkova, N.V., and Ilyin, Yu.V. parallel Dokl. RAN (1992). V. 323, P. 173-177) has been obtained. A comparative analysis of the enzyme and recombinant reverse transcriptase coded by the mobile genome element jockey earlier expressed in a heterological cell system (Ivanov V.V., Melnikov A.A., Siunov A.V., Fodor I.I., Ilyin, Yu.V. parallel EMBO J. (1991), V. 10, P. 2489-2495) has been carried out. Like retroviral RNA-dependent DNA-polymerases, these enzymes show preference for polyribonucleotides and can use poly(rCm) as template. Besides they are inhibited by SH-reagents and require bivalent cations (Mg2+ or Mn2+) and detergent and/or KCl as ionic strength carrier. The enzymes differ drastically from retrovirus reverse transcriptases by a number of catalytic properties (low optima of concentration of requisite cations and ionic strength, strong preference for Mn2+, highly efficiency in using poly(rCm), lack of associated RNase H activity) but exhibit a high degree of similarity among themselves with regard to the above properties. It is suggested that endogenous reverse transcriptase from rat brain is a product of expression of the mobile genome element of the LINE family.