Nucleic Acids Research, 1989, Vol. 17, No. 1 373-387
© 1989
ENZYMOLOGY |
A test of ‘polymerase handover’ as a mechanism for stimulating initiation by RNA polymerase I
Basic Sciences Division, Hutchinson Cancer Research Center 1124 Columbia Street, Seattle, WA 98104, USA
Received July 15, 1988. Revised November 28, 1988. Accepted November 28, 1988.
On the tandemly linked ribosomal genes of Xenopus laevis, the RNA polymerase transcribes past the 3' end of the 4OS coding region and terminates at T3 just upstream of the gene promoter. The close proximity of T3 to the gene promoter, and the functional interdependence of these two elements, has led to the suggestion that polymerase terminating at T3 might be passed directly to the gene promoter. Such a mechanism might be necessary to maintain the characteristic high rate of transcription initiation seen on the ribosomal genes. We have performed a direct test of this model by introducing chain-terminating psoralen adducts into a circular plasmid containing a single gene promoter with its attendant T3 region upstream. We find that the psoralen adducts can completely prevent polymerase from traveling around the template circle (and thus prevent polymerase from approaching the promoter from upstream) without affecting the rate of transcription initiation at the gene promoter. This result suggests that recycling of polymerase from T3 to the promoter is not a significant mechanism in maintaining high initiation rates.
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  B McStay and R H Reeder An RNA polymerase I termination site can stimulate the adjacent ribosomal gene promoter by two distinct mechanisms in Xenopus laevis. Genes & Dev., July 1, 1990; 4(7): 1240 - 1251. [Abstract] [PDF]
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