Identification and characterization of a novel peptide interacting with cAMP-responsive elements binding and cAMP-responsive elements modulator in mouse liver.
OBJECTIVE
Transcription factors coupled to cyclic adenosine mono phosphate (cAMP) signalling in the cAMP-responsive elements binding (CREB)/ATF family constitute a family of activators or repressors that bind to cAMP-responsive promoter elements (CREs) in the regulatory regions of cAMP-inducible genes. A role for CREB/ATF family has been advocated in the control of hepatocellular carcinoma progression. CREB appears to be activated by the X protein of hepatitis B virus, which links to the unphosphorylated form of CREB and activates transcription, thus obviating an otherwise indispensable Ser-133 phosphorylation. Identification of factors capable of triggering transcription via cAMP-responsive elements modulator (CREM)/CREB signalling in the absence of Ser phosphorylation will improve our knowledge of the molecular mechanism of liver cell proliferation.


METHODS
To isolate and study proteins binding and activating CREB and/or CREM in the liver, we performed the screening of a mouse liver cDNA library using the Two-Hybrid System.


RESULTS
We report the identification and characterization of a novel peptide, VTIP-peptide (VTIP-P), which binds and enhances the activation of CREM/CREB, obviating the need for transcription factor phosphorylation. We demonstrated that VTIP-P physically interacts with the activation domain (AD) of the transcription factors CREB/CREM and activates transcription by modifying their phosphorylation pattern in hepatoma cells. The data allowed the conclusion that VTIP-P binds the AD of CREB and CREM by stabilizing their phosphorylation.


CONCLUSIONS
The characterization of molecules capable of interfering in the liver with an important pathway such as CREB could be significant in designing and/or developing new therapeutic approaches to the control of liver cell proliferation.
Brunacci
Cinzia
C
Dipartimento di Medicina Clinica e Sperimentale, Facoltà di Medicina e Chirurgia, Università degli Studi di Perugia, Perugia, Italy.
Piobbico
Danilo
D
Bartoli
Daniela
D
Castelli
Marilena
M
Pieroni
Stefania
S
Bellet
Marina Maria
MM
Viola-Magni
Mariapia
M
Della Fazia
Maria Agnese
MA
Servillo
Giuseppe
G
D000818:Animals; D002352:Carrier Proteins / Q000145:classification / Q000378:metabolism*; D045744:Cell Line, Tumor; D051786:Cyclic AMP Response Element Modulator / Q000235:genetics / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D015723:Gene Library; D008099:Liver / Q000378:metabolism*; D008115:Liver Regeneration / Q000502:physiology*; D051379:Mice; D010455:Peptides / Q000145:classification / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D020798:Two-Hybrid System Techniques
D002352:Carrier Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D010455:Peptides; D014157:Transcription Factors; C551689:VTIP-peptide, mouse; D051786:Cyclic AMP Response Element Modulator