Cloning of a novel gene (ING1L) homologous to ING1, a candidate tumor suppressor

The ING1 gene encodes p33(ING1), a putative tumor suppressor for neuroblastomas and breast cancers, which has been shown to cooperate with p53 in controlling cell proliferation. We have isolated a novel human gene, ING1L, that potentially encodes a PHD-type zinc-finger protein highly homologous to p33(ING1). Fluorescence in situ hybridization and radiation-hybrid analyses assigned ING1L to human chromosome 4. Both ING1 and ING1L are expressed in a variety of human tissues, but we found ING1L expression to be significantly more pronounced in tumors from several colon-cancer patients than in normal colon tissues excised at the same surgical sites. Although the significance of this observation with respect to carcinogenesis remains to be established, the data suggest that ING1L might be involved in colon cancers through interference with signal(s) transmitted through p53 and p33(ING1).     

Polymorphism of the pentanucleotide repeat d(AAAAT) within intron 1 of the human tumor suppressor gene p53 (17p13.1)

DyeDeoxy terminator cycle sequencing of allele-specific polymerase chain reaction products has shown that there is a highly polymorphic d(AAAAT) pentanucleotide repeat within the first intron of the human p53 gene. This provides a genetic marker for tumor suppressor p53 gene alterations.     

The tumor suppressor ING1: structure and function.

The biological functions of the tumor suppressor ING1 have been studied extensively in the past 5 years since it was cloned. Of the three alternatively spliced forms of ING1, p24(ING1) has been the focus of much of past research. Information on the other currently known isoforms, p47(ING1), p32(ING1), and p27(ING1), has been lacking. ING1 shares many biological functions with p53. It has been reported to mediate growth arrest, senescence, apoptosis, anchorage-dependent growth, and chemosensitivity. Some of these functions, such as cell-cycle arrest and apoptosis, have been shown to be dependent on the activity of both ING1 and p53 proteins. In this review, we will examine what is known about ING1 up to this point and clarify the cloning errors originating from the isolation of this gene.     

WWOX, a new potential tumor suppressor gene

BACKGROUND: WWOX (WW domain-containing oxidoreductase) gene, located on chromosome 16q 23.3-24.1 in the region recognized as the common fragile site FRA16D is considered to be a tumor suppressor gene involved in various cancers: breast, ovarian, prostate, esophageal, lung, pancreatic, gastric and hepatic. The aim of this study was to describe (i) putative protein interactions of WWOX (ii) the molecular mechanisms of tumor suppressor activity (iii) present an overview of WWOX in relation to nervous system and breast, prostate and ovarian cancers. METHODS AND RESULTS: WWOX expression is up-regulated in endocrine organs indicating its importance in these tissues. In many cancers WWOX expression is down-regulated and low WWOX expression is related to poor prognosis. CONCLUSION: All the evidence suggest that WWOX can be considered as a new tumor suppressor gene and target for gene therapy due to the association of high WWOX expression with improved disease free survival.     

Microsatellite polymorphism in intron 1 of the bovine myostatin gene

Microsatellites within genes have become important because of their association with genetic diseases in humans. A novel microsatellite was identified in the first intron of the bovine myostatin gene. It is characterized by a mononucleotide core motif that exhibits polymorphic sequence variants (from 12 to 21 repeats) within and between some bovine breeds. Structural analysis of the microsatellite region in bovines as well as in closely related species permitted to trace the possible mechanisms for its structural evolution across the order Artiodactyla.     

The tumor suppressor ING1 contributes to epigenetic control of cellular senescence

Cellular senescence is an effective tumor-suppressive mechanism that causes a stable proliferative arrest in cells with potentially oncogenic alterations. Here, we have investigated the role of the p33ING1 tumor suppressor in the regulation of cellular senescence in human primary fibroblasts. We show that p33ING1 triggers a senescent phenotype in a p53-dependent fashion. Also, endogenous p33ING1 protein accumulates in chromatin in oncogene-senescent fibroblasts and its silencing by RNA interference impairs senescence triggered by oncogenes. Notably, the ability to induce senescence is lost in a mutant version of p33ING1 present in human tumors. Using specific point mutants, we further show that recognition of the chromatin mark H3K4me3 is essential for induction of senescence by p33ING1. Finally, we demonstrate that ING1-induced senescence is associated to a specific genetic signature with a strong representation of chemokine and cytokine signaling factors, which significantly overlaps with that of oncogene-induced senescence. In summary, our results identify ING1 as a critical epigenetic regulator of cellular senescence in human fibroblasts and highlight its role in control of gene expression in the context of this tumor-protective response.     

HaeIII polymorphism in intron 1 of the human p53 gene

A new HaeIII polymorphism, which is found in the first intron of the human p53 gene, provides a genetic marker for tumor suppressor p53 gene alterations.     

3pK, a new mitogen-activated protein kinase-activated protein kinase located in the small cell lung cancer tumor suppressor gene region.

NotI linking clones, localized to the human chromosome 3p21.3 region and homozygously deleted in small cell lung cancer cell lines NCI-H740 and NCI-H1450, were used to search for a putative tumor suppressor gene(s). One of these clones, NL1G210, detected a 2.5-kb mRNA in all examined human tissues, expression being especially high in the heart and skeletal muscle. Two overlapping cDNA clones containing the entire open reading frame were isolated from a human heart cDNA library and fully characterized. Computer analysis and a search of the GenBank database to reveal high sequence identity of the product of this gene to serine-threonine kinases, especially to mitogen-activated protein kinase-activated protein kinase 2, a recently described substrate of mitogen-activated kinases. Sequence identitiy was 72% at the nucleotide level and 75% at the amino acid level, strongly suggesting that this protein is a serine-threonine kinase. Here we demonstrate that the new gene, referred to as 3pK (for chromosome 3p kinase), in fact encodes a mitogen-activated protein kinase-regulated protein serine-threonine kinase with a novel substrate specificity.     

HECT ubiquitin ligase Smurf1 targets the tumor suppressor ING2 for ubiquitination and degradation

Inhibitor of growth 2 (ING2) gene encodes a candidate tumor suppressor and is frequently reduced in many tumors. However, the mechanisms underlying the regulation of ING2, in particular its protein stability, are still unclear. Here we show that the homologous to E6AP carboxyl terminus (HECT)-type ubiquitin ligase Smad ubiquitination regulatory factor 1 (Smurf1) interacts with and targets ING2 for poly-ubiquitination and proteasomal degradation. Intriguingly, the ING2 binding domain in Smurf1 was mapped to the catalytic HECT domain. Furthermore, the C-terminal PHD domain of ING2 was required for Smurf1-mediated degradation. This study provided the first evidence that the stability of ING2 could be regulated by ubiquitin-mediated degradation.

Structured summary

MINT-7894271: ING2 (uniprotkb:Q9H160) binds (MI:0407) to Smurf1 (uniprotkb:Q9HCE7) by pull-down (MI:0096)MINT-7894319, MINT-7894339: ING2 (uniprotkb:Q9H160) physically interacts (MI:0915) with Smurf1 (uniprotkb:Q9HCE7) by anti tag co-immunoprecipitation (MI:0007)MINT-7894301: Smurf1 (uniprotkb:Q9HCE7) physically interacts (MI:0915) with ING2 (uniprotkb:Q9H160) by anti bait co-immunoprecipitation (MI:0006)MINT-7894358: ING1b (uniprotkb:Q9UK53-2) physically interacts (MI:0915) with Smurf1 (uniprotkb:Q9HCE7) by anti tag co-immunoprecipitation (MI:0007)MINT-7894249: ING2 (uniprotkb:Q9H160) physically interacts (MI:0915) with ubiquitin (uniprotkb:P62988) by anti tag co-immunoprecipitation (MI:0007)     

Tethering by lamin A stabilizes and targets the ING1 tumour suppressor

ING proteins interact with core histones through their plant homeodomains (PHDs) and with histone acetyltransferase (HAT) and histone deacetylase (HDAC) complexes to alter chromatin structure. Here we identify a lamin interaction domain (LID) found only in ING proteins, through which they bind to and colocalize with lamin A. Lamin knockout (LMNA(-/-)) cells show reduced levels of ING1 that mislocalize. Ectopic lamin A expression increases ING1 levels and re-targets it to the nucleus to act as an epigenetic regulator. ING1 lacking the LID does not interact with lamin A or affect apoptosis. In LMNA(-/-) cells, apoptosis is not affected by ING1. Mutation of lamin A results in several laminopathies, including Hutchinson-Gilford progeria syndrome (HGPS), a severe premature ageing disorder. HGPS cells have reduced ING1 levels that mislocalize. Expression of LID peptides to block lamin A-ING1 interaction induces phenotypes reminiscent of laminopathies including HGPS. These data show that targeting of ING1 to the nucleus by lamin A maintains ING1 levels and biological function. Known roles for ING proteins in regulating apoptosis and chromatin structure indicate that loss of lamin A-ING interaction may be an effector of lamin A loss, contributing to the HGPS phenotype.     

Methylation of the putative tumor suppressor gene, RASSF1A, in primary cervical tumors

The methylation level of 13 CpG-dinucleotides in the promoter region of the putative tumor suppressor gene RASSF1A (3p21.31) was analyzed in HPV-positive squamous cell carcinomas of cervix using methyl-sensitive restriction endonuclease analysis followed by PCR. The methylation from 3 to 13 CpG-dinucleotides was observed in 64% (25/39) tumors, 22% (2/9) morphologically normal tissues adjacent to tumors (P = 0.0306) and in 2 from 3 leucocytes of peripheral blood of patients. The methylation of these CpG-dinucleotides was absent in DNA of healthy donor leucocytes (0/10). Methylation level of the examined fragment of the RASSF1A promoter region was significantly higher in tumors of patients with lymph node metastases in comparison to tumors of patients without metastases (P = 8.5 x 10(-12)). The methylation frequency of RASSF1A gene was in two times higher than hemi- and homozygous deletion frequency at the region of location of this gene (chromosome 3p21.31), determined earlier. These data suggest that methylation of the RASSF1A gene is one of the main ways of this gene inactivation in HPV-positive cervical squamous cell carcinomas. The methylation of the RASSF1A gene is an early event in genesis of tumor and the level of methylation increased with tumor progression.     

A novel RsaI polymorphism within intron 39 of the neurofibromatosis type 1 (NF1) gene

Familial hypercholesterolemia is caused by mutations in the low density lipoprotein (LDL) receptor gene. Analysis of single-strand conformation polymorphisms of exons 10 and 11 of the LDL receptor gene from familial hypercholesterolemia heterozygotes indicated the presence of two mutations, which were characterized by DNA sequencing. One mutation (N466) was a 3-bp deletion in exon 10 that deletes Asn in codon 466. The other (intron 11_+1,GT) was a splice donor mutation at position +1 of intron 11.     

抑癌基因PTEN及其假基因PTENP1在子宫内膜癌中的研究进展

子宫内膜癌的发病率在逐年上升,引起了人们的广泛关注,但其发病的分子遗传学机制仍不十分清楚。近年来基因改变致癌的研究成为热点。国内外研究报道发现：PTEN（与张力蛋白同源第10染色体丢失的磷酸酶基因）是目前已知的子宫内膜癌中突变率最高的基因,常发生在子宫内膜癌的早期,对其突变的检测有助于子宫内膜癌的早期诊断、治疗及预后评价,并为子宫内膜癌的基因治疗提供了新的靶点。另外,研究发现,PTENP1（PTEN的假基因）转录调控PTEN的表达,被认为与一些肿瘤的发生有关。本文就PTEN基因的结构、功能及在子宫内膜癌中的突变情况、临床意义及PTENP1的研究现状进行综述。