Evidence for gene silencing in Haemophilus influenzae

Evidence for gene silencing of Haemophilus influenzae involved a beta -subu nit of RNA polymerase. The gene presumed silenced was rifampin resistance. The evidence that it was silencing, rather than dominance of a rifampin-sen sitive marker, was that it took place when the rifampin resistance marker w as on both a plasmid and the chromosome, without the presence of a rifampin -sensitive marker, as judged by lack of transformation of a rifampin-resist ant cell to rifampin sensitivity by the plasmid. In addition, three compoun ds that are known to decrease gene silencing in eukaryotes (trichostatin A, sodium butyrate and 5-azacytidine) also decreased the presumed silencing i n H. influenzae. Silencing of rifampin-resistant Escherichia coli did not t ake place with the plasmid from H. influenzae. (C) 2001 Elsevier Science B. V. All rights reserved.