AMY-1, a novel C-MYC binding protein that stimulates transcription activity of C-MYC.
BACKGROUND
The c-myc proto-oncogene has been suggested to play key roles in cell proliferation, differentiation, transformation and apoptosis. A variety of functions of C-MYC, the product of c-myc, are attributed to protein-protein interactions with various cellular factors including Max, YY1, p107, Bin1 and TBP. Max and YY1 bind to the C-terminal region of C-MYC, while p107, Bin1 and TBP bind to the N-terminal region covering myc boxes. The N-terminal region is involved in all the biological functions of C-MYC, and different proteins are therefore thought to interact with the N-terminal region of C-MYC to display different functions.


RESULTS
We cloned two cDNAs which encode a novel C-MYC-binding protein of 11 kDa, designated AMY-1 (Associate of C-MYC). The two cDNAs, AMY-1L and AMY-1S, derived from alternative usage of polyadenylation signals, code for the same protein of 11 kDa. AMY-1 was bound via its C-terminal region to the N-terminal region of C-MYC (amino acids nos 58-148) corresponding to the transactivation domain. AMY-1 was localized in the cytoplasm in cells expressing c-myc at low levels, but in the nucleus in the cells of a high c-myc expression in transiently transfected cells. A similar difference in endogenous AMY-1 localization was observed during the cell cycle: AMY-1 translocated from cytoplasm to nucleus during the S phase when c-myc expression was increased. AMY-1 by itself did not recognize the E-box element, the MYC/Max binding sequence, nor did it transactivate via the element, but stimulated the activation of E-box-regulated transcription by MYC/Max. FISH analyses revealed that the amy-1 gene was located at 1p32.2-1p33 in human genome.


CONCLUSIONS
AMY-1 is a 11 kDa protein which binds to the N-terminal region of C-MYC and stimulates the activation of E-box-dependent transcription by C-MYC. AMY-1, which mostly localizes in the cytoplasm, translocates into the nucleus in the S phase of the cell cycle upon an increase of c-myc expression, and may thus control the transcriptional activity of C-MYC.
Taira
T
T
Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12 Nishi 6, Kita-ku, Sapporo 060 Japan.
Maëda
J
J
Onishi
T
T
Kitaura
H
H
Yoshida
S
S
Kato
H
H
Ikeda
M
M
Tamai
K
K
Iguchi-Ariga
S M
SM
Ariga
H
H
D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism; D002874:Chromosome Mapping; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016259:Genes, myc; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D011485:Protein Binding; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; C000715470:MAS1 protein, human; C116115:MYCBP protein, human; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc; D011994:Recombinant Proteins; D014157:Transcription Factors