Biology:HMGA1

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Short description: Protein-coding gene in the species Homo sapiens


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

High-mobility group protein HMG-I/HMG-Y is a protein that in humans is encoded by the HMGA1 gene.[1][2]

Function

This gene encodes a non-histone chromatin protein involved in many cellular processes, including regulation of inducible gene transcription, DNA replication, heterochromatin organization, integration of retroviruses into chromosomes, and the metastatic progression of cancer cells.

HMGA1 proteins are quite small (~10-12 kDa) and basic molecules, and consist of three AT-hooks with the RGRP (Arg-Gly-Arg-Pro) core motif, a novel cross-linking domain located between the second and third AT-hook, and a C-terminal acidic tail characteristic for the HMG family comprising HMGA, HMGB and HMGN proteins.

HMGA1-GFP fusion proteins are highly dynamic in vivo (determined using FRAP analysis), but in contrast also show nanomolar affinity to AT-rich DNA in vitro (determined biochemically), which might be explained due to the extensive post-transcriptional modifications in vivo. HMGA1 preferentially binds to the minor groove of AT-rich regions in double-stranded DNA using its AT-hooks. It has little secondary structure in solution but assumes distinct conformations when bound to substrates such as DNA or other proteins. HMGA1 proteins have high amounts of diverse posttranslational modifications and are located mainly in the nucleus, especially in heterochromatin, but also in mitochondria and the cytoplasm.

Recently it has been shown that HMGA1 proteins, HMGA1a and HMGA1b, can cross-link DNA fibers in vitro and can induce chromatin clustering in vivo suggesting a structural role of HMGA1 proteins in heterochromatin organization.[3]

At least seven transcript variants encoding two different isoforms (HMGA1a, HMGA1b) have been found for this gene.[4] The splice variant HMGA1c with only two AT hooks and no acidic tail is in discussion to be a real member of the HMGA family.

Mice lacking their variant of HMGA1, i.e., Hmga1-/- mice, are diabetic, show a cardiac hypertrophy and express low levels of the insulin receptor.[5]

Interactions

HMGA1 has been shown to interact with CEBPB[6] and Sp1 transcription factor.[6]

See also

References

  1. ↑ "Organization, inducible-expression and chromosome localization of the human HMG-I(Y) nonhistone protein gene". Nucleic Acids Research 21 (18): 4259–67. Sep 1993. doi:10.1093/nar/21.18.4259. PMID 8414980. 
  2. ↑ "HMGI/Y proteins: flexible regulators of transcription and chromatin structure". Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression 1519 (1–2): 13–29. May 2001. doi:10.1016/S0167-4781(01)00215-9. PMID 11406267. 
  3. ↑ "Cross-linking of DNA through HMGA1 suggests a DNA scaffold". Nucleic Acids Research 39 (16): 7124–33. Sep 2011. doi:10.1093/nar/gkr396. PMID 21596776. 
  4. ↑ "Entrez Gene: HMGA1 high mobility group AT-hook 1". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=3159. 
  5. ↑ "From bending DNA to diabetes: the curious case of HMGA1". Journal of Biology 8 (7): 64. 2009. doi:10.1186/jbiol164. PMID 19664187. 
  6. ↑ 6.0 6.1 "A nucleoprotein complex containing Sp1, C/EBP beta, and HMGI-Y controls human insulin receptor gene transcription". Molecular and Cellular Biology 23 (8): 2720–32. Apr 2003. doi:10.1128/MCB.23.8.2720-2732.2003. PMID 12665574. 

Further reading

External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.



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