The role of GC content in promoting or hindering transcription
This paper suggests the opposite in mammalian cells. Obviously, gene regulation is quite different in prokaryotes, so don't know how much confidence you want to put into that one. 

This paper suggests more of the same, but includes some caveats related to prokaryotes that may pique your interest. They do a pretty in-depth dive of GC content near genes from many different species, but I haven't read it closely enough to give a good breakdown.