The nucleotide sequence of the single Drosophila meianogaster tRNA gene contained in the recombinant plasmid, pDtl20R was determined by the
Maxam and Gilbert method. This plasmid hybridizes to the 90 BC site on the
Val
Drosophila polytene chromosomes, a minor site of tRNA4 hybridization. The
Val
nucleotide sequence of the tRNA4 gene present in pDtl20R differs at four
Val
positions from the sequence expected from that of tRNA4 . The four differences occur at nucleotides 16, 29, 41 and 57 in the coding region. Comparison of the DNA sequence of pDtl20R to that of the plasmid pDt92R, which also hybridizes to the 90 BC site, indicates that the Drosophila fragments contained in these two plasmids are either alleles or repeats. The implications of these findings are discussed.
An in vitro transcription system was developed from a Drosophila Schneider II cell line. This homologous cell-free extract support specific and accurate transcription of various Drosophila tRNA Val genes. The major product of transcription is a tRNA precursor which is processed to a tRNA sized species.
Transfer RNA valine genes originating from different sites on the
Drosophila chromosomes are transcribed at different rates. Comparison of
the sequences in the internal promoter regions of the various genes
indicates that the few differences within the coding regions may not be
responsible for the observed difference in the rates of transcription.
This conclusion is substantiated by studies with hybrid genes constructed
during the course of this work. Preliminary evidence indicates that the Val
tRNA gene which is transcribed at the highest rate may be preceded in its
5'-flanking region by a positively modulating sequence.
Val
The precursor RNAs directed by various tRNA genes are also processed at different rates. Transcription and processing experiments with hybrid
genes suggest that nucleotide changes within the coding region, which do not affect the rate of transcription, influence the rate of processing.
Time course and competition experiments demonstrate that at least two kinetic steps are required for the formation of a stable transcription complex. Studies with an in vitro constructed mutant missing in nucleotides 51-61 in the tRNA coding region suggests that this deleted region (which is highly conserved in eukaryotic tRNAs) may be involved in the primary interaction
required for tRNA gene transcription. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/23673 |
| Date | January 1982 |
| Creators | Rajput, Bhanu |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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