A tRNA gene of Xenopus laevis contains at least two sites promoting transcription

Abstract

A small cloned DNA segment previously shown to contain all genetic information for the expression of the tRNA1met gene of Xenopus laevis was cleaved into an anterior and posterior portion by Hae III restriction. Both restriction fragments were cloned in pCR1 using EcoRI linkers. Starting from these tDNA subclones, a series of new recombinants were constructed. The transcriptional activity of the cloned DNA's was tested both in an in vitro transcriptional system and by means of the oocyte injection technique. It was shown that both the 5' and 3' ends of the cloned gene unit were essential for transcription. We have developed a model for the functional organization of the tRNA1met gene. We propose that the gene contains a regulatory site situated near the 3' portion of the gene unit. For transcription to occur both in vivo and in vitro a specific initiation site near the 5' end of the gene is required.