Regulated nuclear entry of over‐expressed Setdb1. (20th June 2013)

• Record Type: Journal Article
• Authors: Cho, Sunwha; Park, Jung Sun; Kang, Yong‐Kook
• Is Part Of: Genes to cells. Volume 18:Number 8(2013:Aug.)
• Page Start: 694
• Page End: 703
• Publication Date: 2013-06-20
• Subjects: Cytogenetics -- Periodicals; Cells -- Mechanical properties -- Periodicals; Molecular genetics -- Periodicals; Genes -- Periodicals; Molecular biology -- Periodicals; Cytology -- Periodicals; Biomechanics -- Periodicals; 571.6
• DOI: 10.1111/gtc.12068
• Languages: English
• ISSNs: 1356-9597

Abstract

Abstract : Setdb1 is a histone H3‐lysine 9 (H3K9)‐specific methyltransferase that interacts with various transcriptional regulators to induce local heterochromatin formation and participates as an indispensable component in building promyelocytic leukemia nuclear body (PML‐NB), which is involved in various biological processes. We studied the effects of Setdb1 over‐expression. We unexpectedly observed that exogenously expressed GFP‐Setdb1 was retained in the cytoplasm, whereas endogenous Setdb1 showed a punctate nuclear signal. Leptomycin B (LMB) treatment, which blocks protein export from the nucleus, showed that entry of GFP‐Setdb1 to the nucleus was regulated and that GFP‐Setdb1 in the nucleus could localize at PML‐NB as endogenous Setdb1. An analysis of Setdb1 deletion constructs showed that the N‐terminal region was related to the nuclear export of Setdb1; supporting this, we detected two nuclear export signal motifs in this region. This N‐terminal region had a SUMO interaction motif (SIM) whose mutation greatly reduced the ability of Setdb1 to associate with PML‐NB and thus resulted in the disaggregation of PML‐NB structure. We therefore presume that the cytoplasmic retention of over‐expressed Setdb1 occurs as part of a regulatory mechanism to set a tight limit on the nuclear activity of Setdb1, whose excess activity might result in random and haphazard chromatin modifications that cause globally aberrant gene expression.