The effects of ultraviolet irradiation on the transcription of T4 DNA

Procyclic acidic repetitive protein (PARP) genes located in an unusually small alpha-amanitin-resistant transcription unit: PARP promoter activity assayed by transient DNA transfection of Trypanosoma brucei.

“…At any particular UV dose, DNA sequences located further downstream from a promoter are therefore predicted to be more sensitive to UV irradiation than those located closer to the promoter. Measuring the efficiency of RNA polymerase elongation at different UV doses thus allows mapping of a fragment relative to its transcription initiation site (4,(15)(16)(17)40). This method was used by Borst and co-workers (17) to show that the VSG 221 expression site in bloodstream-form trypanosomes is transcribed as a very large (60-kb) polycistronic unit in bloodstream-form T. brucei.…”

Energy Metabolism after U.V.-irradiation in a Sensitive Yeast Strain

“…From the sensitivity of fermentation at an early stage, the size of the structural gene may be estimated (figure 5) . If one assumes that one pyrimidine dimer is sufficient to stop transcription (Michalke andBremer 1969, Sauerbier, Milette andHackett 1970), one calculates a size of about 10 6 dalton using the data of Unrau, Wheatcroft, Cox and Olive (1973) that 48 dimers are formed in the genome of a diploid yeast cells per erg mm 2 . This corresponds to about 3000 nucleotides or a protein with 1000 amino-acid residues .…”

Initiation and Release of RNA by DNA-Dependent RNA Polymerase

“…However, this value is in excellent agreement with the average size calculated for transcription regions in the early genes of T4: From studies on the effect of ultraviolet irradiation of T4 phage on in vivo transcription, we have found these regions to be about 10,000 base pairs in length. 24 Under our low salt assay conditions, each polymerase molecule initiates only one chain, on the average, with most of the RNA being released from the DNA.…”

“…The latter alternative is supported by the observation that the chain length of in vitro-synthesized T4 RNA agrees closely with the calculated size of T4 transcription regions in Vivo. 24 We are hopeful that a definitive answer to this question will come from further characterization of the released product by polyacrylamide gel electrophoresis and 3'-end analysis.…”