HOPX explained

Homeodomain-only protein is a protein that in humans is encoded by the HOPX gene.^[1] It is an important regulator of cardiac development^[2] and a marker of hippocampal neural stem cells.^{[3] [4]}

Function

The protein encoded by this gene is a homeodomain protein that lacks certain conserved residues required for DNA binding. It was reported that choriocarcinoma cell lines and tissues failed to express this gene, which suggested the possible involvement of this gene in malignant conversion of placental trophoblasts. Studies in mice suggested that this protein may interact with serum response factor (SRF) and modulate SRF-dependent cardiac-specific gene expression and cardiac development. Multiple alternatively spliced transcript variants encoding the same protein have been observed, the full-length natures of only some have been determined.

Further reading

• Kook H, Epstein JA . Hopping to the beat. Hop regulation of cardiac gene expression . Trends in Cardiovascular Medicine . 13 . 7 . 261–264 . October 2003 . 14522464 . 10.1016/S1050-1738(03)00107-5 .
• Hartley JL, Temple GF, Brasch MA . DNA cloning using in vitro site-specific recombination . Genome Research . 10 . 11 . 1788–1795 . November 2000 . 11076863 . 310948 . 10.1101/gr.143000 .
• Asanoma K, Matsuda T, Kondo H, Kato K, Kishino T, Niikawa N, Wake N, Kato H . NECC1, a candidate choriocarcinoma suppressor gene that encodes a homeodomain consensus motif . Genomics . 81 . 1 . 15–25 . January 2003 . 12573257 . 10.1016/S0888-7543(02)00011-3 .
• Chen Y, Petersen S, Pacyna-Gengelbach M, Pietas A, Petersen I . Identification of a novel homeobox-containing gene, LAGY, which is downregulated in lung cancer . Oncology . 64 . 4 . 450–458 . 2003 . 12759545 . 10.1159/000070306 . 3205741 .
• Kook H, Lepore JJ, Gitler AD, Lu MM, Wing-Man Yung W, Mackay J, Zhou R, Ferrari V, Gruber P, Epstein JA . Cardiac hypertrophy and histone deacetylase-dependent transcriptional repression mediated by the atypical homeodomain protein Hop . The Journal of Clinical Investigation . 112 . 6 . 863–871 . September 2003 . 12975471 . 193673 . 10.1172/JCI19137 .
• Adu J, Leong FT, Smith NR, Leek JP, Markham AF, Robinson PA, Mighell AJ . Expression of mOb1, a novel atypical 73 amino acid K50-homeodomain protein, during mouse development . Mechanisms of Development . 119 Suppl 1 . Suppl 1 . S43–S47 . December 2002 . 14516659 . 10.1016/S0925-4773(03)00090-X . 119 . 11648378 . free .
• Lemaire F, Millon R, Muller D, Rabouel Y, Bracco L, Abecassis J, Wasylyk B . Loss of HOP tumour suppressor expression in head and neck squamous cell carcinoma . British Journal of Cancer . 91 . 2 . 258–261 . July 2004 . 15213722 . 2409811 . 10.1038/sj.bjc.6601952 .
• Pauws E, Sijmons GG, Yaka C, Ris-Stalpers C . A novel homeobox gene overexpressed in thyroid carcinoma . Thyroid . 14 . 7 . 500–505 . July 2004 . 15307938 . 10.1089/1050725041517020 .
• Toruner GA, Ulger C, Alkan M, Galante AT, Rinaggio J, Wilk R, Tian B, Soteropoulos P, Hameed MR, Schwalb MN, Dermody JJ . Association between gene expression profile and tumor invasion in oral squamous cell carcinoma . Cancer Genetics and Cytogenetics . 154 . 1 . 27–35 . October 2004 . 15381369 . 10.1016/j.cancergencyto.2004.01.026 .
• Asanoma K, Kato H, Inoue T, Matsuda T, Wake N . Analysis of a candidate gene associated with growth suppression of choriocarcinoma and differentiation of trophoblasts . The Journal of Reproductive Medicine . 49 . 8 . 617–626 . August 2004 . 15457851 .
• Wiemann S, Arlt D, Huber W, Wellenreuther R, Schleeger S, Mehrle A, Bechtel S, Sauermann M, Korf U, Pepperkok R, Sültmann H, Poustka A . From ORFeome to biology: a functional genomics pipeline . Genome Research . 14 . 10B . 2136–2144 . October 2004 . 15489336 . 528930 . 10.1101/gr.2576704 .
• Mehrle A, Rosenfelder H, Schupp I, del Val C, Arlt D, Hahne F, Bechtel S, Simpson J, Hofmann O, Hide W, Glatting KH, Huber W, Pepperkok R, Poustka A, Wiemann S . The LIFEdb database in 2006 . Nucleic Acids Research . 34 . Database issue . D415–D418 . January 2006 . 16381901 . 1347501 . 10.1093/nar/gkj139 .
• Kook H, Yung WW, Simpson RJ, Kee HJ, Shin S, Lowry JA, Loughlin FE, Yin Z, Epstein JA, Mackay JP . Analysis of the structure and function of the transcriptional coregulator HOP . Biochemistry . 45 . 35 . 10584–10590 . September 2006 . 16939210 . 10.1021/bi060641s .
• Kee HJ, Kim JR, Nam KI, Park HY, Shin S, Kim JC, Shimono Y, Takahashi M, Jeong MH, Kim N, Kim KK, Kook H . Enhancer of polycomb1, a novel homeodomain only protein-binding partner, induces skeletal muscle differentiation . The Journal of Biological Chemistry . 282 . 10 . 7700–7709 . March 2007 . 17192267 . 10.1074/jbc.M611198200 . free .
• Americo TA, Chiarini LB, Linden R . Signaling induced by hop/STI-1 depends on endocytosis . Biochemical and Biophysical Research Communications . 358 . 2 . 620–625 . June 2007 . 17498662 . 10.1016/j.bbrc.2007.04.202 .

Notes and References

1. Web site: Entrez Gene: HOP homeodomain-only protein.
2. Chen F, Kook H, Milewski R, Gitler AD, Lu MM, Li J, Nazarian R, Schnepp R, Jen K, Biben C, Runke G, Mackay JP, Novotny J, Schwartz RJ, Harvey RP, Mullins MC, Epstein JA . Hop is an unusual homeobox gene that modulates cardiac development . Cell . 110 . 6 . 713–723 . September 2002 . 12297045 . 10.1016/S0092-8674(02)00932-7 . 12189105 . free .
3. Li D, Takeda N, Jain R, Manderfield LJ, Liu F, Li L, Anderson SA, Epstein JA . Hopx distinguishes hippocampal from lateral ventricle neural stem cells . Stem Cell Research . 15 . 3 . 522–529 . November 2015 . 26451648 . 4704104 . 10.1016/j.scr.2015.09.015 .
4. Berg DA, Su Y, Jimenez-Cyrus D, Patel A, Huang N, Morizet D, Lee S, Shah R, Ringeling FR, Jain R, Epstein JA, Wu QF, Canzar S, Ming GL, Song H, Bond AM . A Common Embryonic Origin of Stem Cells Drives Developmental and Adult Neurogenesis . Cell . 177 . 3 . 654–668.e15 . April 2019 . 30929900 . 6496946 . 10.1016/j.cell.2019.02.010 . free .