The C-terminus of the transcriptional co-activator Bob1 (OBF1, OCA-B, POU2AF1) regulates stability

What is it about?

The transcription factor Bob1 is important for proper B-cell function. Mice lacking Bob1 are immunodeficient. Bob1 is generally an unstable protein but the level varies depending on the developmental or activation state of the B-cell. We have found that the charge at the C-terminus of Bob1 can have a dramatic effect on its stability. Post-translational modifications like phosphorylation of the C-terminus may be a way cells regulate their level of Bob1.

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Why is it important?

The mechanism of Bob1 degradation has been suggested to involve the RING-finger SIAH1/2 and ubiquitination. While inhibition of the proteasome stabilizes Bob1, we found no evidence for ubiquitination of Bob1. We show that in B cells, SIAH-proteins are probably not the main regulators of Bob1 stability. We do not know whether proteasomal degradation of Bob1 is direct but we show that the C-terminus acts as a charge-dependent regulator of Bob1 stability.