HEB in the Spotlight: Transcriptional Regulation of T-Cell Specification, Commitment, and Developmental Plasticity
Figure 3
Structure of E-proteins. (a) E-proteins belong to the basic helix-loop-helix (bHLH) family of transcription factors. There are three genes, each encoding for two proteins: HEB (HEBCan and HEBAlt), E2-2 (E2-2Can and E2-2Alt), and E2A (E47 and E12). While E2A proteins are produced by alternative splicing, HEB and E2-2 factors are generated by independent transcription start sites and alternative splicing. All six transcription factors have a basic helix-loop-helix (bHLH) domain, which enables transcription factor dimerization and binding to the DNA. Activation domains 1 (AD1) and AD2 help recruit coactivators to the transcriptional complex. The Alt domain replaces AD1 found in the canonical forms of E-proteins and is conserved between mouse HEBAlt and E2-2Alt as well as through vertebrate evolution. (b) Organization of HEB gene. Vertical grey bars represent exons. Protein domains encoded by exons are shown as horizontal bars. Numbers above exons represent exon numbers, while numbers between exons indicate genomic distance in kb. pDC: plasmacytoid dendritic cells, LMPPs: lymphoid primed multipotent progenitors.
