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Mol. Cell. Biol., Mar 1996, 1256-1266, Vol 16, No. 3
LS Young, N Ahnert and KU Sprague
We have identified a complex between TFIIIB and the upstream promoter of
silkworm tRNA Ala genes that is detectable by gel retardation and DNase I
footprinting. Formation of this complex depends on the integrity of
previously identified upstream promoter elements and on the presence of
other silkworm transcription factors, either TFIIID or a fraction that
contains both TFIIIC and TFIIID. We have used this complex to compare the
interactions of TFIIIB with two kinds of tRNA Ala genes whose different in
vitro transcription properties are conferred by the upstream segments of
their promoters. These are the tRNA C Ala genes, which are transcribed
constitutively, and the tRNA SG Ala genes, which are transcribed only in
the silk gland. We find that TFIIIB binds tRNA SG Ala genes with lower
affinity than it binds tRNA C Ala genes. In addition, the TFIIIB complex
formed on tRNA SG Ala genes differ qualitatively from those formed on tRNA
C Ala genes. Both the transcriptional activity of tRNA SG Ala complexes and
the ability of the complexes to protect upstream DNA from DNase I digestion
are reduced.
Copyright © 1996, American Society for Microbiology
Silkworm TFIIIB binds both constitutive and silk gland-specific tRNA Ala promoters but protects only the constitutive promoter from DNase I cleavage
Institute of Molecular Biology, University of Oregon, Eugene 97403- 1229, USA.
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