Faculty Collaboration Database

SPI-B activates transcription via a unique proline, serine, and threonine domain and exhibits DNA binding affinity differences from PU.1. J Biol Chem 1999 Apr 16;274(16):11115-24

Date

04/10/1999

Pubmed ID

10196196

DOI

10.1074/jbc.274.16.11115

Scopus ID

2-s2.0-0033574423 (requires institutional sign-in at Scopus site)   45 Citations

Abstract

SPI-B is a B lymphocyte-specific Ets transcription factor that shares a high degree of similarity with PU.1/SPI-1. In direct contrast to PU.1(-/-) mice that die in utero and lack monocytes, neutrophils, B cells, and T cells, Spi-B-/- mice are viable and exhibit a severe B cell proliferation defect. Since PU.1 is expressed at wild type levels in Spi-B-/- B cells, the mutant mice provide genetic evidence that SPI-B and PU.1 have at least some non-redundant roles in B lymphocytes. To begin to understand the molecular basis for these defects, we delineated functional domains of SPI-B for comparison to those of PU.1. By using a heterologous co-transfection system, we identified two independent transactivation domains in the N terminus of SPI-B. Interestingly, only one of these domains (amino acids 31-61), a proline/serine/threonine-rich region, unique among Ets proteins, is necessary for transactivation of the immunoglobulin lambda light chain enhancer. This transactivation motif is in marked contrast to PU.1, which contains acidic and glutamine-rich domains. In addition, we describe a functional PU.1 site within the c-FES promoter which SPI-B fails to bind efficiently and transactivate. Finally, we show that SPI-B interacts with the PU.1 cofactors Pip, TBP, c-Jun and with lower affinity to nuclear factor interleukin-6beta and retinoblastoma. Taken together, these data suggest that SPI-B binds DNA with a different affinity for certain sites than PU.1 and harbors different transactivation domains. We conclude that SPI-B may activate unique target genes in B lymphocytes and interact with unique, although currently unidentified, cofactors.

Author List

Rao S, Matsumura A, Yoon J, Simon MC

Author

Sridhar Rao MD, PhD Associate Professor in the Pediatrics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Amino Acid Sequence
Amino Acids
Animals
Base Sequence
DNA Primers
DNA-Binding Proteins
Enhancer Elements, Genetic
Mice
Mutagenesis, Site-Directed
Proline
Promoter Regions, Genetic
Protein-Tyrosine Kinases
Proto-Oncogene Proteins
Proto-Oncogene Proteins c-fes
Serine
Structure-Activity Relationship
Threonine
Trans-Activators
Transcription Factors
Transcriptional Activation