Homodimerization of LDB1 is necessary for activation of the mouse β-major globin gene expression

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NIDDK	EPIGEN/TRANS/CHROM-6

Authors

• I Krivega
• A Dean

Abstract

A multiprotein complex that includes LDB1, TAL1, GATA-1 and LMO2 proteins participates in long-range interaction in the β-globin locus. Reduction of LDB1 using RNAi (LDB1 KD) disrupts long-distant interaction and blocks expression of the β-major globin gene. It is known that the N-terminal dimerization domain (DD) of LDB1 participates in homodimerization of the protein in vitro. We proposed that the DD domain of LDB1 plays a key role in long-range interaction between the LCR and β-major gene promoter. To confirm this hypothesis, LDB1 KD was rescued by expression of LDB1 from transgenic construct with mutation of shRNA target site in LDB1 cDNA. Transgenic LDB1 expression can activate β-major globin gene expression. Several deletions of LDB1 without DD or short conserved sequences in DD were expressed in the background of endogenous LDB1 knock down MEL cells. These deletions were unable to activate β-major globin gene expression. To show a direct role of DD domain in β-major globin gene activation, a fusion protein that contains LMO2 and the DD domain of LDB1 (LMO-DD) was expressed in the LDB1 KD background. LMO-DD fusion protein can rescue LDB1 KD and causes activation of β-major globin gene expression.

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