Modulation of TEL transcription activity by interaction with the ubiquitin-conjugating enzyme UBC9

Abstract

The E-26 transforming specific (ETS)-related gene TEL, also known as ETV6, is involved in a large number of chromosomal rearrangements associated with leukemia and congenital fibrosarcoma. The encoded protein contains two functional domains: a helix-loop-helix (HLH) domain (also known as pointed domain) located at the N terminus and a DNA-binding domain located at the C terminus. The HLH domain is involved in protein-protein interaction with itself and other members of the ETS family of transcription factors such as FLI1. TEL is a transcription factor, and we and others have shown that it is a repressor of gene expression. To understand further the role of TEL in the cell, we have used an in vivo interaction system to identify proteins that interact with TEL. We show that a protein, UBC9, interacts specifically with TEL in vitro and in vivo. UBC9 is a member of the family of ubiquitin-conjugating enzymes. These enzymes usually are involved in proteosomemediated degradation; however, our data suggest that interaction of TEL with UBC9 does not lead to TEL degradation. Our studies show that UBC9 binds to TEL exclusively through the HLH domain of TEL. We also show that TEL expressed as fusion to the DNA-binding domain of Gal4 completely represses a Gal4-responsive promoter, but that the coexpression of UBC9 in the same system restores the activity of the promoter. Targeted point mutation of conserved amino acids in UBC9 essential for enzymatic ubiquitination of proteins does not affect interaction nor transcriptional activity. Based on our data, we conclude that UBC9 physically interacts with TEL through the HLH domain and that the interaction leads to modulation of the transcription activity of TEL.TEL, also known as ETV6, is involved in a large number of chromosomal rearrangements associated with leukemia and congenital fibrosarcoma (1-7). TEL contains two domains: a helix-loop-helix (HLH) domain at the N terminus and a DNA-binding domain [E-26 transforming specific (ETS) domain] at the C terminus. Both domains are conserved in other ETS proteins. The HLH domain is involved in protein-protein interaction, leading to the formation of either a homodimer or heterodimers with other ETS proteins, such as FLI1 (8, 9). TEL is a transcription regulator, and we showed that it is a repressor of gene transcription (6). TEL is expressed in several tissues, but its precise role is not known. The gene often is deleted in patients with leukemia (10). Homozygous deletion of the gene by targeted mutation leads to embryonic death at days E10.5-11.5 because of defective yolk sac angiogenesis (11). Recent studies showed that TEL is the first transcription factor required specifically for hematopoiesis within the bone marrow (12) and support the critical importance of this protein in hematopoiesis.The breakpoints of several chromosomal translocations involving TEL have been cloned, and it was shown that the translocations lead to gene fusion and the expression of chimeric proteins. The chromosomal breakpoints in TEL flank the ...

Transcriptional Activity of Peroxisome Proliferator-activated Receptor γ Is Modulated by SUMO-1 Modification

“…In agreement with our observations, key molecules in the SUMO-1 conjugation system, including SUMO-1, Ubc9, and PIAS, have been shown to modulate the transcriptional activities of p53 (44), androgen receptor (40), aryl hydrocarbon receptor (41), and lymphoid enhancer factor-1 (33) even when these target molecules lacked a major sumoylation site(s) by mutation. Moreover, it has been shown that Ubc9 modulates the transcriptional activity of ETS-1-and TEL-independent of its E2 enzymatic activity (45,46). In view of these reports, a mechanism(s) other than the direct SUMO-1 conjugation to PPAR␥ by Ubc9 and PIASx␤ seem to be important for the regulation of transactivation of PPAR␥.…”

BCL11A is a SUMOylated protein and recruits SUMO‐conjugation enzymes in its nuclear body

“…SUMOylation is necessary for PML to form the nuclear body, where PML collaborates with its functional partners (Shen et al 2006), and interaction with UBC9 and SUMOylation modulates the transcriptional activity and nuclear body assembly of TEL (Chakrabarti et al 1999(Chakrabarti et al , 2000. Abnormalities in SUMO modifying proteins have also been reported.…”

The Aryl Hydrocarbon Receptor Nuclear Transporter Is Modulated by the SUMO-1 Conjugation System

“…The sumoylation of certain key factor(s) such as PML might be crucial for the general mechanism of transcriptional control. Moreover, it was reported that UBC9 modulates transcription by ETS-1 and TEL independent of its enzymatic ability to conjugate them with SUMO-1 (59,60) and that UBC9 mediates the nuclear localization of Vsx-1 without its SUMO-1-conjugating activity (61). Thus, UBC9 may possess some other functions in addition to the role of a SUMO-1-conjugating enzyme.…”