Distinct In Vivo Dynamics of Vertebrate SUMO Paralogues

Ferhan Ayaydin and Mary Dasso*

Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-5431

Monitoring Editor: Joseph Gall

There are three mammalian SUMOparalogues: SUMO-1 is $~$ 45% identical to SUMO-2 and SUMO-3, whichare 96% identical to each other. It is currently unclear whetherSUMO-1, -2 and -3 function in ways that are unique, redundantor antagonistic. To address this question, we examined the dynamicsof individual SUMO paralogues using cell lines that stably expresseach of the mammalian SUMO proteins fused to the yellow fluorescentprotein (YFP). While SUMO-2 and -3 showed very similar distributionsthroughout the nucleoplasm, SUMO-1 was uniquely distributedto the nuclear envelope and to the nucleolus. Photobleachingexperiments revealed that SUMO-1 dynamics were much slower thanSUMO-2 and -3 dynamics. Additionally, the mobility of SUMO paraloguesdiffered between subnuclear structures. Finally, the timingand distributions were dissimilar between paralogues as cellsexited from mitosis. SUMO-1 was recruited to nuclear membraneas nuclear envelopes reformed in late anaphase, and accumulatedrapidly into the nucleus. SUMO-2 and SUMO-3 localized to chromosomeearlier, and accumulated gradually during telophase. Together,these findings demonstrate that mammalian SUMO-1 shows patternsof utilization that are clearly discrete from the patterns ofSUMO-2 and -3 throughout the cell cycle, arguing that it isfunctionally distinct and specifically regulated in vivo.

^*Corresponding author. E-mail: mdasso{at}helix.nih.gov