| SUMO 1 modification of histone deacetylase 1 ( HDAC 1 ) modulates its biological activities . ^^^ Here , in the course of assessing possible post translational modifications of HDAC 1 , we demonstrated that HDAC 1 is a substrate for SUMO 1 ( small ubiquitin related modifier ) modification in vitro and in vivo . ^^^ Together , the results demonstrate that HDAC 1 is modified by SUMO 1 , and this modification can dramatically affect HDAC 1 activity in a number of surrogate biological assays . . ^^^ |