HMGA1 co-activates transcription in B cells through indirect association with DNA.
The immunoglobulin heavy chain enhancer, or mu enhancer, is required for B cell development. Only the appropriate combination of transcription factors results in B cell-specific enhancer activation. HMGA1 (formerly (HMG-I(Y)) is a proposed co-activator of the ETS transcription factors required for mu enhancer activity. HMGA1 associates with the ETS factor PU.1, resulting in changes in PU.1 structure, and enhanced transcriptional synergy with Ets-1 on the mu enhancer in nonlymphoid cells. New data show HMGA1 directly interacts with Ets-1 in addition to PU.1. In vitro HMGA1/Ets-1 interaction facilitates Ets-1/mu enhancer binding in the absence of an HMGA1.Ets-1.DNA complex. To address whether HMGA1 is present in the transcriptionally active mu nucleoprotein complex, we completed DNA pull-down assays to detect protein tethering in the context of protein/DNA interaction. Results show that HMGA1 is not tightly associated with mu enhancer DNA through PU.1 or Ets-1, despite strong associations between these proteins in solution. However, chromatin immunoprecipitation assays show HMGA1 associates with the endogenous enhancer in B cells. Furthermore, antisense HMGA1 substantially decreases mu enhancer activity in B cells. Taken together, these data suggest that HMGA1 functions as a transcriptional mu enhancer co-activator in B cells through indirect association with DNA.
McCarthy
Kevin M
KM
Department of Microbiology, Boston University School of Medicine, Boston, MA 02118, USA.
McDevit
Daniel
D
Andreucci
Amy
A
Reeves
Raymond
R
Nikolajczyk
Barbara S
BS
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000502:physiology; D025741:HMGA1a Protein / Q000378:metabolism / Q000502:physiology*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D051379:Mice; D011485:Protein Binding; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D011994:Recombinant Proteins; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D000099232:Proto-Oncogene Protein Spi-1
D004247:DNA; D025741:HMGA1a Protein; D007143:Immunoglobulin Heavy Chains; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D011994:Recombinant Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000099232:Proto-Oncogene Protein Spi-1; C494042:Ets1 protein, mouse