Gene expression patterns define novel roles for E47 in cell cycle progression, cytokine-mediated signaling, and T lineage development

Abstract

In maturing T lineage cells, the helix-loop-helix protein E47 has been shown to enforce a critical proliferation and developmental checkpoint commonly referred to as ␤ selection. To examine how E47 regulates cellular expansion and developmental progression, we have used an E2A-deficient lymphoma cell line and DNA microarray analysis to identify immediate E47 target genes. Hierarchical cluster analysis of gene expression patterns revealed that E47 coordinately regulates the expression of genes involved in cell survival, cell cycle progression, lipid metabolism, stress response, and lymphoid maturation. These include Plc␥2, Cdk6, CD25, Tox, Gadd45a, Gadd45b, Gfi1, Gfi1b, Socs1, Socs3, Id2, Eto2, and Xbp1. We propose a regulatory network linking Janus kinase (JAK)͞signal transducer and activator of transcription (STAT)-mediated signaling, E47, and suppressor of cytokine signaling (SOCS) proteins in a common pathway. Finally, we suggest that the aberrant activation of Cdk6 in E47-deficient T lineage cells contributes to the development of lymphoid malignancy.L ymphocyte development is regulated, in part, by a distinct class of helix-loop-helix (HLH) proteins, named E proteins (1). Four E proteins, E12, E47, E2-2, and HEB, are expressed in developing lymphocytes. E12 and E47 are encoded by one gene, designated as E2A, and arise through differential splicing in an exon encoding the HLH domain. E2A-deficient mice exhibit a complete block in B cell development at the onset of lineage commitment (2-4). T cell development is partially blocked in E2A-deficient mice before the onset of T cell receptor (TCR) ␤ V(D)J gene rearrangement (5-7).E proteins, and E2A proteins in particular, play critical roles in regulating developmental progression at the pre-TCR and TCR checkpoints (8, 9). Signals emanating from the pre-TCR and TCR complex act to suppress E protein DNA-binding activity, induce the expression of the E protein inhibitor Id3, and lower the abundance of E47 protein levels (10). Lowering the dose of E47 has been demonstrated to release the block in differentiation and proliferation observed in thymocytes with defects in pre-TCR expression and pre-TCR-mediated signaling (8,9,11). The E proteins also function at the TCR checkpoint, because an E2A deficiency has been shown to accentuate positive selection (12). In contrast, positive selection in Id3-ablated mice is blocked, albeit partially (13). Taken together, these data suggest that the E2A proteins act as gatekeepers at the pre-TCR and TCR checkpoints, and passage through these checkpoints requires pre-TCR or TCR-mediated modulation of E2A activity.E proteins also function as tumor suppressors. E2A-deficient mice rapidly develop thymic lymphoma (5, 14). Reintroduction of E2A activity into cell lines adapted from lymphomas that developed in E2A-ablated mice caused rapid apoptosis (15). In contrast, enforced expression of E47 in conjunction with Bcl-2 induced cell cycle arrest, suggesting a direct role for E2A in the suppression of cell growth (11). As a first approach...

MyoD and E-protein heterodimers switch rhabdomyosarcoma cells from an arrested myoblast phase to a differentiated state

“…For example, E47 degradation is regulated by Notch signaling and MAP kinase activity (King et al 2007). In lymphocytes, E2A proteins regulate proliferation and differentiation (Nutt and Kee 2007), and have been shown to regulate cell cycle factors, such as p57 and CDK6 (Rothschild et al 2006;Schwartz et al 2006). Two activation domains, AD1 and AD2, are located at the N-terminal half of the proteins and have both redundant and distinct functions.…”

Targeting CDK6 in cancer: State of the art and new insights

“…[35][36][37] CDK6 is overexpressed in lymphoma, leukemia, glioma, glioblastoma, medulloblastoma, and cancers of squamous cells, salivary gland, bladder, pancreas and prostate. [38][39][40][41][42][43][44][45][46][47][48][49][50] In human prostate cancer cells, CDK6 has also been shown to bind androgen receptor and stimulate its activity in a kinase activity independent manner. 46 Blockage of CDK6 expression by microRNAs (miRNAs) has been shown to inhibit the proliferation of gliomas, medulloblastoma, prostate, bladder, gastric, hepatocellular, and lung cancer cells, indicating the significant role of CDK6 in the initiation and progression of these cancers.…”

Mtg16/Eto2 Contributes to Murine T-Cell Development

“…MTG family members function in transcriptional repression, and therefore, these results imply that E-protein-mediated repression contributes to T-cell development. By comparing gene expression profiles from Mtg16 Ϫ/Ϫ LSK cells (M. Fischer et al, unpublished) to those of genes that were repressed by overexpression of E47 (21,42), we identified 19 genes that were repressed by E47 in hematopoietic progenitor cells but upregulated upon Mtg16 inactivation in LSK cells (see Table S1 in the supplemental material). In addition, we compared the changes in Mtg16 Ϫ/Ϫ gene expression profiles to those in genes regulated by overexpressed E47 in the context of Notch signaling from OP9-DL1 cells (see Table S2 in the supplemental material).…”

“…The experiment was performed twice in triplicate. (C) Venn diagrams are shown that display the intersection between genes upregulated in Mtg16 Ϫ/Ϫ LSK cells relative to wild-type controls and genes upregulated by activated Notch signaling in OP9-DL1 coculture and E47 expression (left panel) (21) or E2A-deficient thymic lymphoma cells that were complemented by reexpressing E47 (right panel) (42 Tables S3 and S4 in the supplemental material). Of note, the expression of Mtg16, but not Mtg8 or Mtgr1, was activated by E47 (21), suggesting a possible regulatory loop between these proteins.…”