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General Comment |
Holewa B, eta l1997 reported that HNF4beta is a new gene of the HNF4 family with distinct activation
and expression profiles in oogenesis and embryogenesis of Xenopus
laevis.
The transcription factor hepatocyte nuclear factor 4 (HNF4) is an orphan member of
the nuclear receptor superfamily expressed in mammals in liver, kidney, and the
digestive tract. The authors isolated the Xenopus homolog of mammalian HNF4 and
revealed that it is not only a tissue-specific transcription factor but also a maternal
component of the Xenopus egg and distributed within an animal-to-vegetal gradient.
It was speculated that this gradient cooperates with the vegetally localized embryonic
induction factor activin A to activate expression of HNF1alpha, a tissue-specific
transcription factor with an expression pattern overlapping that of HNF4. A second Xenopus HNF4 gene, which is more distantly related to
mammalian HNF4 than the previously isolated gene. This new gene was named
HNF4beta to distinguish it from the known HNF4 gene, which is now called
HNF4alpha. HNF4beta is a functional transcription
factor acting sequence specifically on HNF4 binding sites known for HNF4alpha, but
it seems to have a lower DNA binding activity and is a weaker transactivator than the
alpha isoform. Furthermore, the two factors differ with respect to tissue distribution in
adult frogs: whereas HNF4alpha is expressed in liver and kidney, HNF4beta is
expressed in addition in stomach, intestine, lung, ovary, and testis. Both factors are
maternal proteins and present at constant levels throughout embryogenesis. Whereas HNF4alpha is expressed early during oogenesis and is absent in the egg,
HNF4beta is first detected in the latest stage of oogenesis, and transcripts are present
in the egg and early cleavage stages.
NCBI Summary:
The protein encoded by this gene is a nuclear transcription factor which binds DNA as a homodimer. The encoded protein controls the expression of several genes, including hepatocyte nuclear factor 1 alpha, a transcription factor which regulates the expression of several hepatic genes. This gene may play a role in development of the liver, kidney, and intestines. Mutations in this gene have been associated with monogenic autosomal dominant non-insulin-dependent diabetes mellitus type I. At least three different transcript variants encoding three different isoforms have been found for this gene.
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