In vivo footprints between the murine c-myc P1 and P2 promoters.
Assuming that when transcription starts at the P2 promoter of the c-myc gene sites located immediately upstream from P2 are occupied whereas in the absence of initiation they are not, the polymerase chain reaction (PCR)-based method of Mueller & Wold [(1989). Science, 246, 780-786] was used to map in vivo footprints upstream from the P2 promoter in various mouse cell lines. In cultured Friend erythroleukemic cells induced to differentiate with dimethysulfoxide (DMSO), a clear protection corresponding to ME1a2 and E2F sites was observed, consistent with in vitro band-shift and footprint data. However, in cell lines in which the gene was either silent or truncated the footprints were no longer visible. Friend c-myc transcripts decreased to a barely detectable level after 3 h of DMSO treatment. Transcription, as measured by in vitro run-on, was turned off at the level of RNA polymerase elongation rather than initiation [Mechti N., Piechaczyk, M. Blanchard, J.-M., Marty, L., Bonnieu, A., Jeanteur, Ph. & Lebler, B. (1986). Nucleic Acids Res., 24, 9653-9666]. The state of occupancy of the sites did not vary from the first hours up to 9 days of DMSO treatment, suggesting that DNA occupancy per se cannot explain premature termination, which rather would involve a more complex phenomenon.
Plet
A
A
URA CNRS 1191 Génétique moléculaire, Montpellier, France.
Tourkine
N
N
Mechti
N
N
Jeanteur
P
P
Blanchard
J M
JM
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D016259:Genes, myc; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
D004121:Dimethyl Sulfoxide