The L2a element is a mouse CD8 silencer that interacts with MAR-binding proteins SATB1 and CDP.
Previous transgenic-reporter and targeted-deletion studies indicate that the subset-specific expression of CD8αβ heterodimers is controlled by multiple enhancer activities, since no silencer elements had been found within the locus. We have identified such a silencer as L2a, a previously characterized ∼ 220 bp nuclear matrix associating region (MAR) located ∼ 4.5 kb upstream of CD8α. L2a transgenes driven by the E8(I) enhancer showed no reporter expression in thymic subsets or T cells in splenic, inguinal and mesenteric lymph node peripheral T cells. Deletion of L2a resulted in significant reporter de-repression, even in the CD4(+)CD8(+) double positive (DP) thymocyte population. L2a contains binding sites for two MAR-interacting proteins, SATB1 and CDP. We found that that binding of these factors was markedly influenced by the content and spacing of L2a sub-motifs (L and S) and that SATB1 binds preferentially to the L motif both in vitro and in vivo. A small fraction of the transgenic CD8 single positive (SP) thymocytes and peripheral CD8(+) T cells bypassed L2a-silencing to give rise to variegated expression of the transgenic reporter. Crossing the L2a-containing transgene onto a SATB1 knockdown background enhanced variegated expression, suggesting that SATB1 is critical in overcoming L2a-silenced transcription.
Yao
Xin
X
Section of Molecular Genetics and Microbiology, Institute for Cellular and Molecular Biology, University of Texas at Austin, 1 University Station A5000, Austin, TX 78721-0162, USA.
Nie
Hui
H
Rojas
Ingrid C
IC
Harriss
June V
JV
Maika
Shanna D
SD
Gottlieb
Paul D
PD
Rathbun
Gary
G
Tucker
Philip W
PW
D000818:Animals; D001483:Base Sequence; D016827:CD8 Antigens / Q000096:biosynthesis* / Q000235:genetics; D002469:Cell Separation; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000276:immunology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D036961:Matrix Attachment Region Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D034521:Nuclear Matrix-Associated Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D037941:Silencer Elements, Transcriptional / Q000235:genetics*
D016827:CD8 Antigens; C000624101:Cux1 protein, mouse; D018398:Homeodomain Proteins; D036961:Matrix Attachment Region Binding Proteins; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; C469541:Satb1 protein, mouse