Translation of the rat LINE bicistronic RNAs in vitro involves ribosomal reinitiation instead of frameshifting.

AUTOR(ES)

Ilves, H

RESUMO

The genomic structure of the rat LINE (L1Rn) DNA element contains two overlapping open reading frames (ORFs) and apparently has a potential to code for a DNA/RNA-binding protein (in ORF1) and a reverse transcriptase (in ORF2). We have characterized a 1,630-bp L1Rn cDNA clone encompassing the overlapping ORFs and a 600-bp genomic fragment derived from a full-length L1Rn member and containing the beginning of ORF1. These DNAs were used to restore in part the ORF1-ORF2 organization of L1Rn after being cloned into the pSP65 vector under the control of SP6 polymerase promoter. To test whether L1Rn ORF1 and ORF2 are expressed as a fusion protein, a series of capped RNAs with progressive truncations containing one or both ORFs were prepared and translated in the rabbit reticulocyte lysate. Our analysis indicates that the expression of a putative reverse transcriptase-encoded L1Rn ORF2 in vitro is regulated by reinitiation or internal initiation of translation but not by ribosomal frameshifting.

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