Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019163 (hepatitis B)
 38,309 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

For the lymphocytic descendants of the hematopoietic differentiation pathway, characteristic gene rearrangements result in deletions of significant portions of chromosome regions specifying lymphocyte-specific gene products on either or both chromosomes of each involved pair. Molecular mechanisms facilitating the rearrangement/deletion events have been elegantly and fruitfully elaborated in the years since the first documentation of their occurrence by Hozumi and Tonegawa (N. Hozumi and S. Tonegawa, Proc. Natl. Acad. Sci. USA, 73:3628-3632, 1976). Numerous genetic phenomena observed in experiments or the literature suggest to us that specific genome rearrangement/deletion may be characteristic of and necessary for many, perhaps all, differentiating lineages. Thus we propose that on the way to terminal differentiation, cells within a particular lineage must rearrange specific chromosome regions characteristic for that lineage in order to switch off or on, perhaps concomitantly, requisite genes for that differentiation program. Such rearrangements and their ensuing deletions may have been undetected cytogenetically because of small size and/or because normal terminally differentiated cells do not enter mitosis. However, footprints of these rearrangements, most likely in aberrant form, may be preserved in preneoplastic cells and cancer cells of various lineages which exhibit characteristic deletions. An understanding of the cellular recombinational machinery involved in normal physiological genome rearrangements such as we propose may clarify some puzzling aspects of current theories concerning retinoblastoma, Wilms' tumor, and other "deletion syndromes" and the role of parental genome imprinting [B. M. Cattanach and M. Kirk, Nature (Lond.), 315: 496-498, 1985; C. Sapienza et al., Nature (Lond.), 328: 251-254, 1987; D. Solter, Annu. Rev. Genet., 22: 127-146, 1988]. The recombinatorial activity, when inappropriately expressed in dividing cells (i.e., cells which should be terminally differentiated but are still cycling for various reasons) could be responsible for such diverse phenomena as large deletions; chromosomal translocations into commonly deleted regions; amplicons; apparent nonrandom chromosome integration of viral genomes such as hepatitis B, human papilloma virus, papovaviruses, and retroviruses; and the observation of fragile sites. It could explain why these various phenomena often involve the same restricted regions of the genome. Some clues and consequences integral to the proposal are discussed.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Lineage-specific gene rearrangement/deletion: a nonconservative model. 266 39

There is considerable interest in the 11p13 region because of its involvement in Wilms tumor, sporadic aniridia, and other congenital abnormalities. Cloned DNA sequences from this region might be useful in understanding the chromosomal abnormalities which lead to such disorders. However, few such markers exist. Using somatic cell hybrids which contain defined 11p deletions, two cloned DNA sequences which flank a deletion generated in an hepatocellular carcinoma (as a consequence of hepatitis B virus integration) were mapped to 11p13. Thus both ends of the deletion observed in an hepatocellular carcinoma are within 11p13.
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PMID:Sequences which flank an 11p deletion observed in an hepatocellular carcinoma map to 11p13. 302 49

Malignant transformation from mortal, normal cells to immortal, cancer cells is generally associated with activation of telomerase and subsequent telomere maintenance. A major mechanism to regulate telomerase activity in human cells is transcriptional control of the telomerase catalytic subunit gene, human telomerase reverse transcriptase (hTERT). Several transcription factors, including oncogene products (e.g. c-Myc) and tumor suppressor gene products (e.g. WT1 and p53), are able to control hTERT transcription when over-expressed, although it remains to be determined whether a cancer-associated alteration of these factors is primarily responsible for the hTERT activation during carcinogenic processes. Microcell-mediated chromosome transfer experiments have provided evidence for endogenous factors that function to repress the telomerase activity in normal cells and are inactivated in cancer cells. At least one of those endogenous telomerase repressors, which is encoded by a putative tumor suppressor gene on chromosome 3p, acts through transcriptional repression of the hTERT gene. The hTERT gene is also a target site for viruses frequently associated with human cancers, such as human papillomavirus (HPV) and hepatitis B virus (HBV). HPV E6 protein contributes to keratinocyte immortalization and carcinogenesis through trans-activation of the hTERT gene transcription. In at least some hepatocellular carcinomas, the hTERT gene is a non-random integration site of HBV genome, which activates in cis the hTERT transcription. Thus, a variety of cellular and viral oncogenic mechanisms converge on transcriptional control of the hTERT gene. Regulation of chromatin structure through the modification of nucleosomal histones may mediate the action of these cellular and viral mechanisms. Further elucidation of the hTERT transcriptional regulation, including identification and characterization of the endogenous repressor proteins, should lead to better understanding of the complex regulation of human telomerase in normal and cancer cells and may open up new strategies for anticancer therapy.
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PMID:Transcriptional regulation of the telomerase hTERT gene as a target for cellular and viral oncogenic mechanisms. 1280 29

The protein encoded by the hepatitis B viral X-gene, HBx, is essential for viral infection and has been shown to regulate gene transcription and the Ras signaling pathway including Raf, MEK, and ERK. To better understand regulatory mechanism of HBx functions, we investigated whether ERK1/2-induced phosphorylation of HBx regulates its transcriptional activity on p21(WAF1/Cip1) promoter. HBx-genotype A (WT1) and its modified HBx (WT2; (38)SSPSPS(43) in WT1 was substituted by (38)PPSSPS(43) in HBx-genotype F) were phosphorylated by ERK1/2 in vitro, although their Ser --> Ala constructs, SA1 (S(43) of WT1 to A) and SA2 (S(41) of WT2 to A), were not. HBx WT1 and WT2, but not SA2, repressed transcription from the p21(WAF1/Cip1) promoter. This repression was blocked by treatment with PD98059, an inhibitor of MEK, or by overexpression of dominant negative MEK1. Furthermore, WT1 and WT2 localized predominantly in the nucleus, whereas SA1 and SA2 localized to the cytoplasm, suggesting that the subcellular localization of HBx is controlled by its phosphorylation. Overall, our findings provide insight that ERK1/2-mediated phosphorylation of HBx regulates HBx function and localization, and may contribute to dysregulation of cell cycle progression leading to hepatocarcinogenesis in HBV-infected cells.
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PMID:Subcellular localization and transcriptional repressor activity of HBx on p21(WAF1/Cip1) promoter is regulated by ERK-mediated phosphorylation. 1518 45

The fragility of the evidence for SV40 association with human cancer is seen in studies of NHL. A publication in 1999 stated that SV40 is rarely present in NHL. In 2002, two laboratories reported SV40 sequences in 42% to 43% of cases of NHL . One of these laboratories also detected SV40 sequences in small proportions of pediatric tumors (e.g., Wilm's tumor, hepatoblastoma, rhabdomyosarcoma, medulloblastoma, osteosarcoma, and retinoblastoma) and adult carcinomas (e.g., lung, colon, breast, and prostate) These positive results were not confirmed in subsequent studies published in 2003. Capello et al and Mackenzie et al failed to detect SV40 sequences in NHL tissues. Sanjose et al examined sera from patients with NHL and from controls for antibodies reactive to SV40 VLPs, and they detected no significant differences between the two groups. The association of SV40 with NHL is in doubt. An etiologic link between a virus and a cancer becomes plausible when evidence from different lines of enquiry (e.g., epidemiology, pathogenesis, and molecular mechanisms) is mutually reinforcing and together provides a coherent picture that can connect the biology the virus to the characteristics of the disease. The associations of human papillomaviruses with cervical cancer and hepatitis B and C viruses with hepatocellular carcinoma are examples in which the etiologic link is clear. With SV40 and mesothelioma, the data on viral sequences in tumors is inconsistent and disputed, and serologic evidence does not support any association. The epidemiologic data do not show that documented exposures tt SV40 increase the risk of mesothelioma. It seems improbable that a single virus (which cannot be conclusively demonstrated to be present in the community) contributes to the development of such a wide variety of tumors, spanning all age groups and histologic types. The weaknesses in the evidence linking SV40 with mesothelioma are summarized in Box 11 It seems unlikely that infection with SV40 contributes to the development of human mesothelioma or any other human cancer.
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PMID:Causality of mesothelioma: SV40 question. 1555 56