title: Sumoylation is important for stability, subcellular localization, and transcriptional activity of SALL4, an essential stem cell transcription factor.
abstract: SALL4 is a transcription factor that plays a key role in the maintenance and self-renewal of embryonic stem cells and hematopoietic stem cells. Given that little is known about regulation of SALL4, we studied biochemical modifications of SALL4B, a major splicing variant of SALL4, and elucidated their biological function. SALL4B was primarily modified by ubiquitination when it was expressed in both Sf9 and HEK293T cells. A significant fraction of SALL4B was further modified by sumoylation when it was expressed in HEK293T cells. Constitutive SUMO-modification of SALL4B was also detected in Tera-1, a cell line of the teratocarcinoma origin. SALL4B sumoylation was independent of ubiquitination and lysine residues 156, 316, 374, and 401 were essential for sumoylation. Chromatin fraction contained more SUMO-deficient SALL4B. Despite a shorter half-life than the wild-type counterpart, SUMO-deficient SALL4B interacted with OCT4 more efficiently than the wild-type SALL4B. RNAi-mediated silencing of SALL4 expression caused significant down-regulation of both OCT4 and SOX2, which was rescued by ectopic expression of SALL4B but not by SUMO-deficient mutant. Significantly, compared with the wild-type SALL4B, SUMO-deficient mutant exhibited compromised trans-activation or trans-repression activities in reporter gene assays. Combined, our studies reveal sumoylation as a novel form of post-translational modification for regulating the stability, subcellular localization, and transcriptional activity of SALL4.
authors.affiliation: Department of Environmental Medicine, New York University Langone Medical Center, 57 Old, Forge Road, Tuxedo, New York 10987, USA.
authors.forename: Feikun
authors.initials: F
authors.lastname: Yang
authors.forename: Yixin
authors.initials: Y
authors.lastname: Yao
authors.forename: Yongping
authors.initials: Y
authors.lastname: Jiang
authors.forename: Luo
authors.initials: L
authors.lastname: Lu
authors.forename: Yupo
authors.initials: Y
authors.lastname: Ma
authors.forename: Wei
authors.initials: W
authors.lastname: Dai
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D017930:Genes, Reporter; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D008239:Lysine / Q000737:chemistry; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D034622:RNA Interference; D013234:Stem Cells / Q000166:cytology*; D058207:Sumoylation; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; C472575:SALL4 protein, human; D014157:Transcription Factors; D008239:Lysine