Abstract
A human DNA library, cloned in bacteriophage lambda, was screened with an opal suppressor tRNA probe. Two genes were isolated, subcloned into pBR322, and sequenced. One is a normal opal suppressor tRNA gene 87 nucleotides in length without intervening sequences. It has a TCA anticodon demonstrating that the mature tRNA reads the termination codon UGA. The 5' internal control region for transcription has two extra nucleotides compared to the consensus sequence for eucaryotic tRNA genes, while the 3' internal control region is normal. This gene differs from a previously sequenced chicken opal suppressor serine tRNA gene (Hatfield, D., Dudock, B., and Eden, F. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 4940-4944) only at position 11. The second human gene appears to be a pseudogene truncated near the 3' end, since in the cloverleaf form of the mature tRNA there are three noncomplementary bases in the acceptor stem. The two human genes have a high degree of homology and, excluding the truncated 3' terminus of the pseudogene, differ in only two positions. The flanking sequences of the pseudogene are about 90% homologous to the consensus sequence of the human Alu family of repeated sequences. This gene appears to have been inserted between two adjacent Alu family members.
Highlights
A humanDNA library, cloned in bacteriophage X, Misreading of termination codons by majorcytoplasmic was screened with anopal suppressor tRNA probe.Two tRNAshas beenobserved in highereucaryotic cells
Suppressor tRNAs toform phosphoseryl-tRNA suggests that they havea specialized function in highereucaryotes
The occurrence and role of prompted us toisolate and sequence the gene or genes encodnonsense suppressor tRNAs are just beginning to be under- ing them from the genomes of several higher eucaryotes
Summary
Vol 260,No.4,Issue of February 25,pp. 2501-2508,1385 Printed in U.S.A. - From the Laboratoryof Molecular CarcinoEenesis.National Cancer Institute, National Institutes of Health, Bethesda, Maryland20205. Two opal suppressor serine tRNAs, which occur in mammalian, avian, and amphibiancells [15, 16], are examples of naturally occurring nonsense suppressor tRNAs inhigher eucaryotes Sequences of these tRNAs from bovine liver [15, 16] and thesequence of one of these tRNAsfrom human and from mouse cells [17] have shownthat they ar9e0 nucleotides in length and that they contafienw modified bases. The fact that nonsense suppressor tRNAs function aannd initial studyw,e sequenced an opal suppressor serine tRNA thatnonsensesuppressortRNA genes are expressed and gene from the chicken genome [18] It was 87 nucleotides in function in higher eucaryotes has been demonstrated by: 1) length and contained a TCA anticodon. § Supported by United States Public Health Service Grant J F32 CA7348-0154 BI-3 awarded by the National Cancer Institute, De-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
