Biomedical subjects

Negusse Habtemichael

Publications and source records attributed to Negusse Habtemichael.

4 recordsLinked to original sources

PubMed2006

The Survivin-Crm1 interaction is essential for chromosomal passenger complex localization and function.

The chromosomal passenger complex (CPC) of Aurora-B, Borealin, INCENP (inner centromere protein) and Survivin coordinates essential chromosomal and cytoskeletal events during mitosis. Here, we show that the nuclear export receptor Crm1 is crucially involved in tethering the CPC to the centromere by interacting with a leucine-rich nuclear export signal (NES), evolutionarily conserved in all mammalian Survivin proteins. We show that inhibition of the Survivin-Crm1 interaction by treatment with leptomycin B or by RNA-interference-mediated Crm1 depletion prevents centromeric targeting of Survivin. The genetic inactivation of the Survivin-Crm1 interaction by mutation of the NES affects the correct localization and function of Survivin and the CPC during mitosis. By contrast, CPC assembly does not seem to require the Survivin-Crm1 interaction. Our report shows the functional significance of the Survivin-Crm1 interface and provides a novel link between the mitotic effector Crm1 and the CPC.

Cell Line, Tumor↗

PubMed2006

Nuclear export is essential for the tumor-promoting activity of survivin.

Survivin appears to function as an apoptosis inhibitor and a regulator of cell division during development and tumorigenesis. Here we report the molecular characterization of the nucleocytoplasmic transport of survivin and its potential implications for tumorigenesis. We identified an evolutionary conserved Crm1-dependent nuclear export signal (NES) in survivin. In dividing cells, the NES is essential for tethering survivin and the survivin/Aurora-B kinase complex to the mitotic machinery, which in turn appears to be essential for proper cell division. In addition, export seems to be required for the cytoprotective activity of survivin, as export-deficient survivin fails to protect tumor cells against chemo- and radiotherapy-induced apoptosis. These findings appear to be clinically relevant since preferential nuclear localization of survivin correlated with enhanced survival in colorectal cancer patients. Targeting survivin's nuclear export by the application of NES-specific antibodies promoted its nuclear accumulation and inhibited its cytoprotective function. We demonstrate that nuclear export is essential for the biological activity of survivin and promote the identification of molecular decoys to specifically interfere with survivin's nuclear export as potential anticancer therapeutics.

Apoptosis↗

PubMed2005

Patient-based cross-platform comparison of oligonucleotide microarray expression profiles.

The comparison of gene expression measurements obtained with different technical approaches is of substantial interest in order to clarify whether inter-platform differences may conceal biologically significant information. To address this concern, we analyzed gene expression in a set of head and neck squamous cell carcinoma patients, using both spotted oligonucleotide microarrays made from a large collection of 70-mer probes and commercial arrays produced by in situ synthesis of sets of multiple 25-mer oligonucleotides per gene. Expression measurements were compared for 4425 genes represented on both platforms, which revealed strong correlations between the corresponding data sets. Of note, a global tendency towards smaller absolute ratios was observed when using the 70-mer probes. Real-time quantitative reverse transcription PCR measurements were conducted to verify expression ratios for a subset of genes and achieved good agreement regarding both array platforms. In conclusion, similar profiles of relative gene expression were obtained using arrays of either single 70-mer or multiple short 25-mer oligonucleotide probes per gene. Although qualitative assessments of the expression of individual genes have to be made with caution, our results indicate that the comparison of gene expression profiles generated on these platforms will help to discover disease-related gene signatures in general.

Base Sequence↗

PubMed2002

Cloning the AFURS1 gene which is up-regulated in senescent human parenchymal kidney cells.

To study the changes in gene expression in senescent cells we applied the suppression subtractive hybridization of two cDNA pools isolated from human parenchymal kidney cells in the phase of exponential growth and cellular senescence in vitro. In addition to several genes known to be associated with cellular senescence, we identified a new gene, which is overexpressed in senescent kidney parenchymal cells. The full-length cDNA consists of 5226 nucleotides with an open reading frame (ORF) encoding 701 amino acids (Accession number: AJ306929). The gene product has a predicted molecular mass of 77.31 kDa. The ORF of the new gene shows significant homology to P-type ATPase family gene products and therefore was called AFURS1 (ATPase family homolog up-regulated in senescence cells). The consensus sequence phosphorylation site (DKTGTLT) is highly conserved. According to the GenBank database AFURS1 is mapped to the sequence segment NT_005535.3 at chromosomal region 3q26.32 and has 18 exons. The AFURS1 gene might have a role in cellular aging and tumor suppression as well.

Adenosine Triphosphatases↗