CCAAT/enhancer binding protein alpha uses distinct domains to prolong pituitary cells in the growth 1 and DNA synthesis phases of the cell cycle

BMC Cell Biol. 2002 Mar 21;3:6. doi: 10.1186/1471-2121-3-6.


Background: A number of transcription factors coordinate differentiation by simultaneously regulating gene expression and cell proliferation. CCAAT/enhancer binding protein alpha (C/EBPalpha) is a basic/leucine zipper transcription factor that integrates transcription with proliferation to regulate the differentiation of tissues involved in energy balance. In the pituitary, C/EBPalpha regulates the transcription of a key metabolic regulator, growth hormone.

Results: We examined the consequences of C/EBPalpha expression on proliferation of the transformed, mouse GHFT1-5 pituitary progenitor cell line. In contrast to mature pituitary cells, GHFT1-5 cells do not contain C/EBPalpha. Ectopic expression of C/EBPalpha in the progenitor cells resulted in prolongation of both growth 1 (G1) and the DNA synthesis (S) phases of the cell cycle. Transcription activation domain 1 and 2 of C/EBPalpha were required for prolongation of G1, but not of S. Some transcriptionally inactive derivatives of C/EBPalpha remained competent for G1 and S phase prolongation. C/EBPalpha deleted of its leucine zipper dimerization functions was as effective as full-length C/EBPalpha in prolonging G1 and S.

Conclusion: We found that C/EBPalpha utilizes mechanistically distinct activities to prolong the cell cycle in G1 and S in pituitary progenitor cells. G1 and S phase prolongation did not require that C/EBPalpha remained transcriptionally active or retained the ability to dimerize via the leucine zipper. G1, but not S, arrest required a domain overlapping with C/EBPalpha transcription activation functions 1 and 2. Separation of mechanisms governing proliferation and transcription permits C/EBPalpha to regulate gene expression independently of its effects on proliferation.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • CCAAT-Enhancer-Binding Protein-alpha / genetics
  • CCAAT-Enhancer-Binding Protein-alpha / metabolism
  • CCAAT-Enhancer-Binding Protein-alpha / physiology*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / physiology
  • Cell Line, Transformed
  • Centromere / genetics
  • DNA / biosynthesis*
  • G1 Phase / genetics
  • G1 Phase / physiology*
  • Gene Targeting
  • Green Fluorescent Proteins
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Mice
  • Pituitary Gland / cytology
  • Pituitary Gland / metabolism*
  • Pituitary Gland / physiology*
  • Protein Interaction Mapping
  • Protein Structure, Tertiary / genetics
  • Protein Structure, Tertiary / physiology
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • S Phase / genetics
  • S Phase / physiology
  • Stem Cells / chemistry
  • Stem Cells / metabolism
  • Stem Cells / physiology
  • Transcriptional Activation / genetics
  • Transcriptional Activation / physiology


  • CCAAT-Enhancer-Binding Protein-alpha
  • Cell Cycle Proteins
  • Luminescent Proteins
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • DNA