Multiple forms of C/EBPβ bind the EFII enhancer sequence in the rous sarcoma virus long terminal repeat

Rosalie Sears, Linda Sealy

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

In this report we demonstrate that C/EBPβ is a major component of three EFII DNA binding complexes, EFIIa, EFIIb, and EFIIc, which we have previously shown to specifically recognize a C/EBP consensus binding site found in the EFII enhancer sequence from the Rous sarcoma virus long terminal repeat (R. C. Sears and L. Sealy, J. Virol. 66:6338-6352, 1992). Three different forms of C/EBPβ, p42, p35, and p20, can bind the EFII DNA sequence as homodimers, and dimerization experiments show that EFIIa is a homodimer of p20 C/EBPβ, EFIIb is primarily composed of a p20/p35 heterodimer with minor amounts of p20/p42 heterodimer and p35 homodimer, and EFIIc is composed of p20 and/or p35 heterodimerized with a novel 60-kDa protein. p20 C/EBPβ is likely equivalent to the internally initiated translation product of C/EBPβ, LIP (liver inhibitor protein), described by P. Descombes and U. Schibler (Cell 67:569-579, 1991). In contrast to the low level of LIP expressed in liver, postulated to occur because of leaky ribosome scanning, we found high levels of expression of p20 C/EBPβ in fibroblasts and lymphocytes. In murine fibroblasts, p20 C/EBPβ has an extended half-life, four times longer than those of p42 and p35 C/EBPβ, which could contribute to its abundant accumulation in this cell type, even though its synthesis by leaky ribosome scanning might be inefficient. Interestingly, overexpression of either the long or short form of C/EBPβ represses EFII-mediated transcription, suggesting that another unidentified EFII transactivator(s) exists, which may be dominantly inhibited by C/EBPβ proteins, and/or that transactivation by C/EBPβ proteins requires posttranslational modifications that were lacking in the transient overexpression experiments.

Original languageEnglish (US)
Pages (from-to)4855-4871
Number of pages17
JournalMolecular and Cellular Biology
Volume14
Issue number7
StatePublished - Jul 1994
Externally publishedYes

Fingerprint

Rous sarcoma virus
Terminal Repeat Sequences
CCAAT-Enhancer-Binding Proteins
Ribosomes
Liver
Fibroblasts
Proteins
Trans-Activators
Dimerization
Post Translational Protein Processing
Transcriptional Activation
Half-Life
Binding Sites
Lymphocytes
DNA

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

Multiple forms of C/EBPβ bind the EFII enhancer sequence in the rous sarcoma virus long terminal repeat. / Sears, Rosalie; Sealy, Linda.

In: Molecular and Cellular Biology, Vol. 14, No. 7, 07.1994, p. 4855-4871.

Research output: Contribution to journalArticle

@article{1062a741aa19432895987e6b41483723,
title = "Multiple forms of C/EBPβ bind the EFII enhancer sequence in the rous sarcoma virus long terminal repeat",
abstract = "In this report we demonstrate that C/EBPβ is a major component of three EFII DNA binding complexes, EFIIa, EFIIb, and EFIIc, which we have previously shown to specifically recognize a C/EBP consensus binding site found in the EFII enhancer sequence from the Rous sarcoma virus long terminal repeat (R. C. Sears and L. Sealy, J. Virol. 66:6338-6352, 1992). Three different forms of C/EBPβ, p42, p35, and p20, can bind the EFII DNA sequence as homodimers, and dimerization experiments show that EFIIa is a homodimer of p20 C/EBPβ, EFIIb is primarily composed of a p20/p35 heterodimer with minor amounts of p20/p42 heterodimer and p35 homodimer, and EFIIc is composed of p20 and/or p35 heterodimerized with a novel 60-kDa protein. p20 C/EBPβ is likely equivalent to the internally initiated translation product of C/EBPβ, LIP (liver inhibitor protein), described by P. Descombes and U. Schibler (Cell 67:569-579, 1991). In contrast to the low level of LIP expressed in liver, postulated to occur because of leaky ribosome scanning, we found high levels of expression of p20 C/EBPβ in fibroblasts and lymphocytes. In murine fibroblasts, p20 C/EBPβ has an extended half-life, four times longer than those of p42 and p35 C/EBPβ, which could contribute to its abundant accumulation in this cell type, even though its synthesis by leaky ribosome scanning might be inefficient. Interestingly, overexpression of either the long or short form of C/EBPβ represses EFII-mediated transcription, suggesting that another unidentified EFII transactivator(s) exists, which may be dominantly inhibited by C/EBPβ proteins, and/or that transactivation by C/EBPβ proteins requires posttranslational modifications that were lacking in the transient overexpression experiments.",
author = "Rosalie Sears and Linda Sealy",
year = "1994",
month = "7",
language = "English (US)",
volume = "14",
pages = "4855--4871",
journal = "Molecular and Cellular Biology",
issn = "0270-7306",
publisher = "American Society for Microbiology",
number = "7",

}

TY - JOUR

T1 - Multiple forms of C/EBPβ bind the EFII enhancer sequence in the rous sarcoma virus long terminal repeat

AU - Sears, Rosalie

AU - Sealy, Linda

PY - 1994/7

Y1 - 1994/7

N2 - In this report we demonstrate that C/EBPβ is a major component of three EFII DNA binding complexes, EFIIa, EFIIb, and EFIIc, which we have previously shown to specifically recognize a C/EBP consensus binding site found in the EFII enhancer sequence from the Rous sarcoma virus long terminal repeat (R. C. Sears and L. Sealy, J. Virol. 66:6338-6352, 1992). Three different forms of C/EBPβ, p42, p35, and p20, can bind the EFII DNA sequence as homodimers, and dimerization experiments show that EFIIa is a homodimer of p20 C/EBPβ, EFIIb is primarily composed of a p20/p35 heterodimer with minor amounts of p20/p42 heterodimer and p35 homodimer, and EFIIc is composed of p20 and/or p35 heterodimerized with a novel 60-kDa protein. p20 C/EBPβ is likely equivalent to the internally initiated translation product of C/EBPβ, LIP (liver inhibitor protein), described by P. Descombes and U. Schibler (Cell 67:569-579, 1991). In contrast to the low level of LIP expressed in liver, postulated to occur because of leaky ribosome scanning, we found high levels of expression of p20 C/EBPβ in fibroblasts and lymphocytes. In murine fibroblasts, p20 C/EBPβ has an extended half-life, four times longer than those of p42 and p35 C/EBPβ, which could contribute to its abundant accumulation in this cell type, even though its synthesis by leaky ribosome scanning might be inefficient. Interestingly, overexpression of either the long or short form of C/EBPβ represses EFII-mediated transcription, suggesting that another unidentified EFII transactivator(s) exists, which may be dominantly inhibited by C/EBPβ proteins, and/or that transactivation by C/EBPβ proteins requires posttranslational modifications that were lacking in the transient overexpression experiments.

AB - In this report we demonstrate that C/EBPβ is a major component of three EFII DNA binding complexes, EFIIa, EFIIb, and EFIIc, which we have previously shown to specifically recognize a C/EBP consensus binding site found in the EFII enhancer sequence from the Rous sarcoma virus long terminal repeat (R. C. Sears and L. Sealy, J. Virol. 66:6338-6352, 1992). Three different forms of C/EBPβ, p42, p35, and p20, can bind the EFII DNA sequence as homodimers, and dimerization experiments show that EFIIa is a homodimer of p20 C/EBPβ, EFIIb is primarily composed of a p20/p35 heterodimer with minor amounts of p20/p42 heterodimer and p35 homodimer, and EFIIc is composed of p20 and/or p35 heterodimerized with a novel 60-kDa protein. p20 C/EBPβ is likely equivalent to the internally initiated translation product of C/EBPβ, LIP (liver inhibitor protein), described by P. Descombes and U. Schibler (Cell 67:569-579, 1991). In contrast to the low level of LIP expressed in liver, postulated to occur because of leaky ribosome scanning, we found high levels of expression of p20 C/EBPβ in fibroblasts and lymphocytes. In murine fibroblasts, p20 C/EBPβ has an extended half-life, four times longer than those of p42 and p35 C/EBPβ, which could contribute to its abundant accumulation in this cell type, even though its synthesis by leaky ribosome scanning might be inefficient. Interestingly, overexpression of either the long or short form of C/EBPβ represses EFII-mediated transcription, suggesting that another unidentified EFII transactivator(s) exists, which may be dominantly inhibited by C/EBPβ proteins, and/or that transactivation by C/EBPβ proteins requires posttranslational modifications that were lacking in the transient overexpression experiments.

UR - http://www.scopus.com/inward/record.url?scp=0028239102&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0028239102&partnerID=8YFLogxK

M3 - Article

C2 - 8007984

AN - SCOPUS:0028239102

VL - 14

SP - 4855

EP - 4871

JO - Molecular and Cellular Biology

JF - Molecular and Cellular Biology

SN - 0270-7306

IS - 7

ER -