BS69 undergoes SUMO modification and plays an inhibitory role in muscle and neuronal differentiation.

BS69, an adenovirus E1A binding protein, has been described as a co-repressor in association with various transcription factors. But its characteristics and exact biological functions remain largely unknown at present. Now we intensively investigated the localization of BS69 and its various truncated derivatives and found that: (a) BS69 forms oligomer through its C-terminus and (b) both PHD and MYND domain are important for the localization of BS69. Furthermore, we provided evidence showing that BS69 interacts with PIAS1 (a well-characterized SUMO E3 enzyme) and Ubc9 (the only SUMO E2 enzyme so far identified) through its distinct regions. And PIAS1 significantly increases the SUMO modification of BS69. More importantly, in terms of the biological function of BS69, we found that BS69 plays an inhibitory role in the muscle and neuronal differentiation process. By taking advantage of several PHD and MYND domain mutants of BS69, we found that the PHD domain plays indispensable roles in the localization, sumoylation and function of BS69. Thus, our work contributed to the more intensive understanding of BS69.