GENES, VARIANT GENES, AND PSEUDOGENES OF THE HUMAN TRANSFER RNAVAL GENE FAMILY ARE DIFFERENTIALLY EXPRESSED IN HELA-CELLS AND IN HUMAN PLACENTA

Pre-tRNAsVal were identified in unfractionated tRNA preparations from HeLa cells and human placenta and their 5′ leader structures were deduced from the nucleotide sequences of the corresponding cDNAs. Several of these precursors can be assigned to nine out of the eleven members of the human tRNAVal gene family characterized so far, which demonstrates that these gene loci are actively transcribed in vivo. Among the expressed genes there are (a) genes for the two known tRNAVal isoacceptor species from human placenta, (b) gene variants that exhibit sequence alterations as compared to conventional genes, and (C) pseudogenes that produce processing-deficient precursors which are not matured to tRNAs. The transcription products of several yet unknown tRNAVal genes have also been detected. Furthermore, different expression patterns are observed in the two cell types studied. These data allow for the first time an insight into the in vivo expression of a human tRNA gene family. © 1990 Oxford University Press.