Inhibitory effect of the mi transcription factor encoded by the mutant mi allele on GA binding protein-mediated transcript expression in mouse mast cells.
The mi transcription factor (MITF) is a basic-helix-loop-helix leucine zipper (bHLH-Zip) transcription factor that is important for the development of mast cells. Mast cells of mi/mi genotype express normal amounts of abnormal MITF (mi-MITF), whereas mast cells of tg/tg genotype do not express any MITFs. The synthesis of heparin is abnormal in the skin mast cells of mi/mi mice. Because N-deacetylase/N-sulfotransferase 2 (NDST-2) is essential for the synthesis of heparin, the amount of NDST-2 messenger RNA (mRNA) was compared among cultured mast cells (CMCs) of +/+, mi/mi, and tg/tg genotypes. The NDST-2 mRNA was detected by in situ hybridization in the skin mast cells of +/+ and tg/tg mice, but not in the skin mast cells of mi/mi mice. The amount of NDST-2 mRNA decreased significantly in CMCs derived from mi/mi mice when compared to the values of +/+ and tg/tg mice, suggesting that the defective form of MITF inhibited the expression of the NDST-2 transcript. The expression of NDST-2 transcript was mediated by the GGAA motif located in the 5'-untranslated region. GA binding protein (GABP) bound the GGAA motif and increased the amount of NDST-2 transcript. The mi-MITF appeared to inhibit the ability of GABP to express NDST-2 transcript by disturbing its nuclear localization. This is the first study to show that expression of an abnormal form of a bHLH-Zip transcription factor can dramatically alter the intracellular location of another DNA/RNA binding factor, which in turn brings about profound and unexpected consequences on transcript expression.
Morii
E
E
Department of Pathology, Osaka University Medical School, Suita, Japan. morii@patho.med.osaka-u.ac.jp
Ogihara
H
H
Oboki
K
K
Sawa
C
C
Sakuma
T
T
Nomura
S
S
Esko
J D
JD
Handa
H
H
Kitamura
Y
Y
D020121:5' Untranslated Regions; D000483:Alleles; D000581:Amidohydrolases / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology*; D005260:Female; D051268:GA-Binding Protein Transcription Factor; D015870:Gene Expression; D018257:Helix-Loop-Helix Motifs; D006493:Heparin / Q000096:biosynthesis; D017403:In Situ Hybridization; D008297:Male; D008407:Mast Cells / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D051739:Microphthalmia-Associated Transcription Factor; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D012867:Skin / Q000201:enzymology; D015238:Sulfotransferases / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*
D020121:5' Untranslated Regions; D004268:DNA-Binding Proteins; D051268:GA-Binding Protein Transcription Factor; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D012333:RNA, Messenger; D014157:Transcription Factors; D006493:Heparin; D004247:DNA; C491855:Ndst2 protein, mouse; D015238:Sulfotransferases; D000581:Amidohydrolases