Islet beta-cell-specific MafA transcription requires the 5'-flanking conserved region 3 control domain.
MafA is a key transcriptional activator of islet beta cells, and its exclusive expression within beta cells of the developing and adult pancreas is distinct among pancreatic regulators. Region 3 (base pairs -8118 to -7750 relative to the transcription start site), one of six conserved 5' cis domains of the MafA promoter, is capable of directing beta-cell-line-selective expression. Transgenic reporters of region 3 alone (R3), sequences spanning regions 1 to 6 (R1-6; base pairs -10428 to +230), and R1-6 lacking R3 (R1-6(DeltaR3)) were generated. Only the R1-6 transgene was active in MafA(+) insulin(+) cells during development and in adult cells. R1-6 also mediated glucose-induced MafA expression. Conversely, pancreatic expression was not observed with the R3 or R1-6(DeltaR3) line, although much of the nonpancreatic expression pattern was shared between the R1-6 and R1-6(DeltaR3) lines. Further support for the importance of R3 was also shown, as the islet regulators Nkx6.1 and Pax6, but not NeuroD1, activated MafA in gel shift, chromatin immunoprecipitation (ChIP), and transfection assays and in vivo mouse knockout models. Lastly, ChIP demonstrated that Pax6 and Pdx-1 also bound to R1 and R6, potentially functioning in pancreatic and nonpancreatic expression. These data highlight the nature of the cis- and trans-acting factors controlling the beta-cell-specific expression of MafA.
Raum
Jeffrey C
JC
Vanderbilt University Medical Center, Department of Molecular Physiology and Biophysics, Nashville, TN 37232, USA.
Hunter
Chad S
CS
Artner
Isabella
I
Henderson
Eva
E
Guo
Min
M
Elghazi
Lynda
L
Sosa-Pineda
Beatriz
B
Ogihara
Takeshi
T
Mirmira
Raghavendra G
RG
Sussel
Lori
L
Stein
Roland
R
D024506:5' Flanking Region; D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D002478:Cells, Cultured; D005136:Eye Proteins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D051473:Maf Transcription Factors, Large / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000378:metabolism; D011485:Protein Binding; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism; D014158:Transcription, Genetic
D051792:Basic Helix-Loop-Helix Proteins; D005136:Eye Proteins; D005947:Glucose; D018398:Homeodomain Proteins; D051473:Maf Transcription Factors, Large; D009419:Nerve Tissue Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; C491328:Nkx6-1 protein, mouse; C000605730:PAX6 protein, human; C000605732:Pax6 protein, mouse; C093564:Neurogenic differentiation factor 1