Cloning and characterization of a novel gene, striamin, that interacts with the tumor suppressor protein p53

Expression analysis of a novel cDNA isolated from immortal murine fibroblasts revealed a single transcript of 3.0 kilobase pairs that was highly expressed in mouse and human striated muscle and in mouse heart. The gene has therefore been named striamin. Its expression was confined to skeletal muscle types with a fast glycolytic (2B) contractile phenotype. It was also detected in C2C12 mouse myoblasts and was down-regulated during in vitro myogenesis. The cDNA has a single open reading frame encoding a predicted 16.8-kDa protein of 149 amino acids with no homology to known proteins. Microinjection and transfection of green fluorescence protein-tagged striamin demonstrated that it localizes to the nucleus. Coimmunoprecipitations revealed that it can interact with p53 (a positive marker for myoblast differentiation) in vivo and in vitro. Furthermore, it repressed p53 activity in p53-mediated reporter assays. Fluorescence in situ hybridization with a mouse P1 genomic clone localized the gene to chromosome 12C3, which is syntenic to human chromosome 14q21-22

The Heumann-Hotzel model for aging revisited

Since its proposition in 1995, the Heumann-Hotzel model has remained as an obscure model of biological aging. The main arguments used against it were its apparent inability to describe populations with many age intervals and its failure to prevent a population extinction when only deleterious mutations are present. We find that with a simple and minor change in the model these difficulties can be surmounted. Our numerical simulations show a plethora of interesting features: the catastrophic senescence, the Gompertz law and that postponing the reproduction increases the survival probability, as has already been experimentally confirmed for the Drosophila fly.Comment: 11 pages, 5 figures, to be published in Phys. Rev.

CRISPR screens identify gene targets at breast cancer risk loci

Background: Genome-wide association studies (GWAS) have identified > 200 loci associated with breast cancer risk. The majority of candidate causal variants are in noncoding regions and likely modulate cancer risk by regulating gene expression. However, pinpointing the exact target of the association, and identifying the phenotype it mediates, is a major challenge in the interpretation and translation of GWAS. Results: Here, we show that pooled CRISPR screens are highly effective at identifying GWAS target genes and defining the cancer phenotypes they mediate. Following CRISPR mediated gene activation or suppression, we measure proliferation in 2D, 3D, and in immune-deficient mice, as well as the effect on DNA repair. We perform 60 CRISPR screens and identify 20 genes predicted with high confidence to be GWAS targets that promote cancer by driving proliferation or modulating the DNA damage response in breast cells. We validate the regulation of a subset of these genes by breast cancer risk variants. Conclusions: We demonstrate that phenotypic CRISPR screens can accurately pinpoint the gene target of a risk locus. In addition to defining gene targets of risk loci associated with increased breast cancer risk, we provide a platform for identifying gene targets and phenotypes mediated by risk variants.Natasha K. Tuano, Jonathan Beesley, Murray Manning, Wei Shi, Laura Perlaza, Jimenez, Luis F. Malaver, Ortega, Jacob M. Paynter, Debra Black, Andrew Civitarese, Karen McCue, Aaron Hatzipantelis, Kristine Hillman, Susanne Kaufmann, Haran Sivakumaran, Jose M. Polo, Roger R. Reddel, Vimla Band, Juliet D. French, Stacey L. Edwards, David R. Powell, Georgia Chenevix, Trench, and Joseph Rosenblu

Downregulation of metallothionein-IIA expression occurs at immortalization

Metallothioneins (MTs) may modulate a variety of cellular processes by regulating the activity of zinc-binding proteins, These proteins have been implicated in cell growth regulation, and their expression is abnormal in some tumors. In particular, MT-IIA is expressed 27-fold less in human colorectal tumors and tumor cell lines compared with normal tissue (Zhang et al,, 1997), Here we demonstrate that MT-IIA downregulation occurs when human cells become immortal, a key event in tumorigenesis, After immortalization MT-IIA expression remains inducible but the basal activity of the MT-IIA promoter is decreased, MT-IIA downregulation at immortalization is one of the most common immortalization-related changes identified to date, suggesting that MT-IIA has a role in this process

Synthetic lethality of cytolytic HSV-1 in cancer cells with ATRX and PML deficiency

Cancers that utilize the alternative lengthening of telomeres (ALT) mechanism for telomere maintenance are often difficult to treat and have a poor prognosis. They are also commonly deficient for expression of ATRX protein, a repressor of ALT activity, and a component of promyelocytic leukemia nuclear bodies (PML NBs) that are required for intrinsic immunity to various viruses. Here, we asked whether ATRX deficiency creates a vulnerability in ALT cancer cells that could be exploited for therapeutic purposes. We showed in a range of cell types that a mutant herpes simplex virus type 1 (HSV-1) lacking ICP0, a protein that degrades PML NB components including ATRX, was ten- to one thousand-fold more effective in infecting ATRX-deficient cells than wild-type ATRX-expressing cells. Infection of co-cultured primary and ATRX-deficient cancer cells revealed that mutant HSV-1 selectively killed ATRX-deficient cells. Sensitivity to mutant HSV-1 infection also correlated inversely with PML protein levels, and we showed that ATRX upregulates PML expression at both the transcriptional and post-transcriptional levels. These data provide a basis for predicting, based on ATRX or PML levels, which tumors will respond to a selective oncolytic herpesvirus.Mingqi Han, Christine E. Napier, Sonja Frölich, Erdahl Teber, Ted Wong, Jane R. Noble, Eugene H.Y. Choi, Roger D. Everett, Anthony J. Cesare, and Roger R. Redde