Nucleolin is one component of the B cell-specific transcription factor and switch region binding protein, LR1

LR1 is a B cell-specific, sequence-specific DNA binding activity that regulates transcription in activated B cells. LR1 also binds Ig heavy chain switch region sequences and may function in class switch recombination. LR1 contains two polypeptides, of 106 kDa and 45 kDa, and here we report that the...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1997-04, Vol.94 (8), p.3605-3610
Main Authors: Hanakahi, L A, Dempsey, L A, Li, M J, Maizels, N
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
B-Lymphocytes - immunology
Biochemistry
Biological Sciences
Cell Line
Deoxyribonucleic acid
DNA
DNA-Binding Proteins - genetics
DNA-Binding Proteins - immunology
Genes
Humans
Immunoglobulin Class Switching
Immunoglobulin Switch Region - genetics
Mice
Molecular Sequence Data
Nuclear Proteins - genetics
Nuclear Proteins - immunology
Nucleolin
Peptides
Phosphoproteins - genetics
Phosphoproteins - immunology
RNA-Binding Proteins
Transcription Factors - genetics
Transcription Factors - immunology
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Summary:LR1 is a B cell-specific, sequence-specific DNA binding activity that regulates transcription in activated B cells. LR1 also binds Ig heavy chain switch region sequences and may function in class switch recombination. LR1 contains two polypeptides, of 106 kDa and 45 kDa, and here we report that the 106-kDa component of LR1 is nucleolin. This identification, initially made by microsequence analysis, was verified by showing that ( i ) LR1–DNA binding activity increased in B cells transfected with a nucleolin cDNA expression construct; ( ii ) LR1–DNA binding activity was recognized by antibodies raised against recombinant human nucleolin; and ( iii ) in B cells transfected with epitope-tagged nucleolin expression constructs, the LR1–DNA complex was recognized by the anti-tag antibody. Nucleolin is an abundant nucleolar protein which is believed to play a role in rDNA transcription or organization, or rRNA processing. Homology between nucleolin and histone H1 suggests that nucleolin may alter DNA organization in response to cell cycle controls, and the nucleolin component of LR1 may therefore function to organize switch regions before, during, or after switch recombination. The demonstration that nucleolin is a component of a B cell-specific complex that binds switch region sequences suggests that the G-rich switch regions may have evolved from rDNA. Ig rDNA recombination
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.94.8.3605