Conservation of the COP9/signalosome in budding yeast

Background The COP9/signalosome (CSN), a multiprotein complex consisting of eight subunits, is implicated in a wide variety of regulatory processes including cell cycle control, signal transduction, transcriptional activation, and plant photomorphogenesis. Some of these functions have been linked to CSN-associated enzymes, including kinases and an activity that removes the ubiquitin-like protein NEDD8/Rub1p from the cullin subunit of E3 ligases. CSN is highly conserved across species from fission yeast to humans, but sequence comparison has failed to identify the complex in budding yeast, except for a putative CSN5 subunit called Rri1p.