• Register
Forgot Password

If you have forgotten your password you can enter your email here and get a temporary password sent to your email.


Leaving Community

Are you sure you want to leave this community? Leaving the community will revoke any permissions you have been granted in this community.


NFI-B3, a novel transcriptional repressor of the nuclear factor I family, is generated by alternative RNA processing.

Nuclear factor I (NFI) proteins constitute a family of sequence-specific transcription factors whose functional diversity is generated through transcription from four different genes (NFI-A, NFI-B, NFI-C, and NFI-X), alternative RNA splicing, and protein heterodimerization. Here we describe a naturally truncated isoform, NFI-B3, which is derived from the human NFI-B gene, in addition to characterizing further human NFI-B1 and NFI-B2, two differentially spliced variants previously isolated from hamster and chicken. Although NFI-B1 and NFI-B2 proteins are translated from an 8. 7-kilobase message, the mRNA for NFI-B3 has a size of only 1.8 kilobases. The NFI-B3 message originates from the failure to excise the first intron downstream of the exons encoding the DNA binding domain and subsequent processing of this transcript at an intron-internal polyadenylation signal. The translation product includes the proposed DNA binding and dimerization domain and terminates after translation of two additional "intron" encoded codons. In SL-2 cells, which are void of endogenous NFI, NFI-B3 by itself had no effect on transcriptional regulation and failed to bind DNA. Coexpression of NFI-B3 with other isoforms of the NFI-B, -C, and -X family, however, led to a strong reduction of transcriptional activation compared with the expression of these factors alone. Gel shift analysis indicated that NFI-B3 disrupts the function of other NFI proteins by reducing their DNA binding activity by heterodimer formation. The efficiency of NFI-B3 heterodimers to bind to DNA correlated with the degree of transcriptional repression. The abundance of NFI-B transcripts varied significantly between different human cell lines and tissues, suggesting a potential involvement of these factors in the complex mechanisms that generate cell type specificity.

Pubmed ID: 9099724


  • Liu Y
  • Bernard HU
  • Apt D


The Journal of biological chemistry

Publication Data

April 18, 1997

Associated Grants


Mesh Terms

  • Alternative Splicing
  • Animals
  • CCAAT-Enhancer-Binding Proteins
  • Cell Line
  • Cell Nucleus
  • Chickens
  • Cloning, Molecular
  • Cricetinae
  • DNA-Binding Proteins
  • Exons
  • Genetic Variation
  • HeLa Cells
  • Humans
  • Introns
  • NFI Transcription Factors
  • Nuclear Proteins
  • Polymerase Chain Reaction
  • Protein Biosynthesis
  • RNA, Messenger
  • Recombinant Proteins
  • Repressor Proteins
  • Transcription Factors
  • Transcription, Genetic
  • Y-Box-Binding Protein 1