Y. Jubete et al., HLYM, A TRANSCRIPTIONAL SILENCER DOWNSTREAM OF THE PROMOTER IN THE HLY OPERON OF ESCHERICHIA-COLI, Journal of bacteriology, 177(1), 1995, pp. 242-246
Transcription of the hly operon of transmissible plasmids in Escherich
ia coli is subject to a tight regulation which also involves various c
hromosomal genes, such as hha. We have identified a 200-bp region with
in the hlyC gene, designated hlyM, which modulates hemolysin expressio
n, The deletion of hlyM increased the activity of hly::galK fusion 20
fold. hlyM does not contain any internal promoter, nor is it capable o
f acting in trans, Our data suggest that the chromosomal Hha protein i
nteracts with hlyM in order to silence the hly promoter, In addition,
hlyR, a positive activator of hemolysin expression, seems to suppress
the modulatory effect dictated by the Hha protein on the hlyM region.