SMAR1 and Cux/CDP modulate chromatin and act as negative regulators of the TCRbeta enhancer (Ebeta).
Chromatin modulation at various cis-acting elements is critical for V(D)J recombination during T and B cell development. MARbeta, a matrix-associated region (MAR) located upstream of the T cell receptor beta (TCRbeta) enhancer (Ebeta), serves a crucial role in silencing Ebeta-mediated TCR activation. By DNaseI hypersensitivity assays, we show here that overexpression of the MAR binding proteins SMAR1 and Cux/CDP modulate the chromatin structure at MARbeta. We further demonstrate that the silencer function of MARbeta is mediated independently by SMAR1 and Cux/CDP as judged by their ability to repress Ebeta-dependent reporter gene expression. Moreover, the repressor activity of SMAR1 is strongly enhanced in the presence of Cux/CDP. These two proteins physically interact with each other and colocalize within the perinuclear region through a SMAR1 domain required for repression. The repression domain of SMAR1 is separate from the MARbeta binding domain and contains a nuclear localization signal and an arginine-serine (RS)-rich domain, characteristic of pre-mRNA splicing regulators. Our data suggest that at the double positive stage of T cell development, cis-acting MARbeta elements recruit the strong negative regulators Cux and SMAR1 to control Ebeta-mediated recombination and transcription.
Kaul-Ghanekar
Ruchika
R
National Center for Cell Science, Ganeshkhind, Pune 411007, India.
Jalota
Archana
A
Pavithra
L
L
Tucker
Philip
P
Chattopadhyay
Samit
S
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000737:chemistry; D002843:Chromatin / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D020868:Gene Silencing; D018398:Homeodomain Proteins; D006801:Humans; D036961:Matrix Attachment Region Binding Proteins / Q000737:chemistry / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D017434:Protein Structure, Tertiary; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000032:analysis / Q000502:physiology*; D014157:Transcription Factors; D014158:Transcription, Genetic
C417914:BANP protein, human; C080632:CUX1 protein, human; D018797:Cell Cycle Proteins; D002843:Chromatin; C000624101:Cux1 protein, mouse; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D036961:Matrix Attachment Region Binding Proteins; D009687:Nuclear Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D012097:Repressor Proteins; C076189:SATB1 protein, human; D014157:Transcription Factors