TY - JOUR
T1 - Novel activator protein-2α splice-variants function as transactivators of the ovine placental lactogen gene
AU - Limesand, Sean W.
AU - Anthony, Russell V.
PY - 2001
Y1 - 2001
N2 - Activator protein-2 (AP-2) has been implicated as a transactivator of the human and ovine placental lactogen (oPL) genes. Transcriptional enhancement through an AP-2 cis-acting element has been described for other genes expressed in the placenta, but the AP-2 isoform enhancing expression is species dependent. Transactivation of the oPL minimal promoter (-124 bp to +16 bp) by AP-2 was confirmed by mutational analysis in transiently transfected human choriocarcinoma cells (BeWo). AP-2α was localized in ovine chorionic epithelial cells by immunohistochemistry and a 3-kb transcript was identified by Northern hybridization. Four nearly full-length AP-2 cDNAs were isolated from an ovine placenta cDNA library. Nucleotide sequencing these cDNAs revealed that the AP-2 mRNA expressed in the ovine placenta shares identity with human AP-2α, but variations in the predicted N-terminus were observed, and three unique AP-2α splice-variants were identified. Expression of AP-2α variants in HepG2 cells, devoid of endogenous AP-2, indicates that enhancement through the AP-2 element in the oPL gene minimal promoter was variant dependent. RNA transcripts for all of the ovine AP-2α splice-variants were confirmed in ovine placenta by RT-PCR, and homologs for two variants were found in human placenta. However, only one AP-2α transcript, which shares identity to Xenopus AP-2α, was expressed in BeWo cells. Immunoblot analysis confirmed AP-2α variants in ovine chorionic binucleate cell nuclear extracts, one of which migrates similar to the AP-2α variant identified in BeWo cell nuclear extracts. These data indicate the presence of new mammalian AP-2α splice-variants that augment transactivation of the oPL gene in ovine chorionic binucleate cells.
AB - Activator protein-2 (AP-2) has been implicated as a transactivator of the human and ovine placental lactogen (oPL) genes. Transcriptional enhancement through an AP-2 cis-acting element has been described for other genes expressed in the placenta, but the AP-2 isoform enhancing expression is species dependent. Transactivation of the oPL minimal promoter (-124 bp to +16 bp) by AP-2 was confirmed by mutational analysis in transiently transfected human choriocarcinoma cells (BeWo). AP-2α was localized in ovine chorionic epithelial cells by immunohistochemistry and a 3-kb transcript was identified by Northern hybridization. Four nearly full-length AP-2 cDNAs were isolated from an ovine placenta cDNA library. Nucleotide sequencing these cDNAs revealed that the AP-2 mRNA expressed in the ovine placenta shares identity with human AP-2α, but variations in the predicted N-terminus were observed, and three unique AP-2α splice-variants were identified. Expression of AP-2α variants in HepG2 cells, devoid of endogenous AP-2, indicates that enhancement through the AP-2 element in the oPL gene minimal promoter was variant dependent. RNA transcripts for all of the ovine AP-2α splice-variants were confirmed in ovine placenta by RT-PCR, and homologs for two variants were found in human placenta. However, only one AP-2α transcript, which shares identity to Xenopus AP-2α, was expressed in BeWo cells. Immunoblot analysis confirmed AP-2α variants in ovine chorionic binucleate cell nuclear extracts, one of which migrates similar to the AP-2α variant identified in BeWo cell nuclear extracts. These data indicate the presence of new mammalian AP-2α splice-variants that augment transactivation of the oPL gene in ovine chorionic binucleate cells.
KW - Activator protein-2 (AP-2)
KW - Ovine
KW - Placental lactogen gene
KW - Transcriptional regulation
KW - Trophoblast
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U2 - 10.1046/j.1432-1327.2001.02124.x
DO - 10.1046/j.1432-1327.2001.02124.x
M3 - Article
C2 - 11298758
AN - SCOPUS:0035006824
SN - 0014-2956
VL - 268
SP - 2390
EP - 2401
JO - European Journal of Biochemistry
JF - European Journal of Biochemistry
IS - 8
ER -