Biomedical subjects

A Affaitati

Publications and source records attributed to A Affaitati.

4 recordsLinked to original sources

PubMed2001

Identification of alternative splicing of spinocerebellar ataxia type 2 gene.

Spinocerebellar ataxia 2 (SCA-2) is a neurodegenerative disorder caused by the expansion of an unstable CAG/polyglutamine repeat located at the NH(2)-terminus of ataxin-2 protein. Ataxin-2 is composed by 1312 aminoacids and it is expressed ubiquitously in human tissues. To date, the function of ataxin-2 is not known. In this study, we report the characterization of an alternative splice variant of human ataxin-2. The splice transcript lacks the exon 21 and connects exon 20 to exon 22 with the same reading frame of the full length mRNA. This novel isoform of ataxin-2 is conserved in the mouse. It is named type IV to differentiate it from type II splice variant lacking exon 10 (present in human and mouse cDNAs) and from type III, lacking exon 10 and exon 11 seen in mouse. Type IV of human ataxin-2 cDNA is predicted to encode a protein of 1294 residues. Both the full length and the type IV transcript of ataxin-2 are present in several human tissues, including brain, spinal cord, cerebellum, heart and placenta. These findings allow the hypothesis that type I, II and IV of human ataxin-2 might perform different functions.

Alternative Splicing↗

PubMed2000

Polyglutamine-mediated aggregation and cell death.

The expansion of CAG repeats is the genetic defect underlying eight neurodegenerative diseases. A common feature of these disorders is the presence of intracellular aggregates in neuronal cells. It is still unclear the significance of these cellular inclusions in the neurodegenerative process, since cell death without aggregate formation has been reported. We have constructed a synthetic fusion protein containing 17 or 43 CAG repeats and the green fluorescent protein that recapitulates the features of CAG-expanded alleles. Expression of 43, but not 17 CAG repeats results in formation of nuclear aggregates in human neuroblastoma cells. Moreover, the normal allele (17 CAG) is sequestered in the inclusion bodies. The presence of nuclear inclusions tightly correlates with apoptosis in cells expressing the protein encoding 43 CAG repeats. Cells harboring nuclear aggregates stop proliferation and undergo apoptosis. Moreover, the inhibition of protein degradation pathway increases intracellular aggregates and cell death. These data indicate that intranuclear aggregates induce apoptosis and suggest that the degradation of unfolded proteins improves cell survival.

Alleles↗

PubMed1999

The length of polyglutamine tract, its level of expression, the rate of degradation, and the transglutaminase activity influence the formation of intracellular aggregates.

A common feature of CAG-expansion neurodegenerative diseases is the presence of intranuclear aggregates in neuronal cells. We have used a synthetic fusion protein containing at the NH2 terminus the influenza hemoagglutinin epitope (HA), a polyglutamine stretch (polyQ) of various size (17, 36, 43 CAG) and a COOH tail encoding the green fluorescent protein (GFP). The fusion proteins were expressed in COS-7 and neuroblastoma SK-N-BE cells. We found that the formation of aggregates largely depends on the length of polyglutamine tracts and on the levels of expression of the fusion protein. Moreover, transglutaminase overexpression caused an increase of insoluble aggregates only in cells expressing the mutant expanded protein. Conversely, treatment of cells with cystamine, a transglutaminase inhibitor, reduced the percentage of aggregates. We found also that the inhibition of the proteasome ubiquitin-dependent degradation increased the formation of intranuclear aggregates. These data suggest that length of polyglutamine tract, its expression, unbalance between cellular transglutaminase activity, and the ubiquitin-degradation pathway are key factors in the formation of intranuclear aggregates.

Acetylcysteine↗

PubMed1997

The S.//.A.IG amino acid motif is present in a replication dependent late H3 histone variant of P. lividus sea urchin.

A novel gene encoding a new H3 histone varian (H3L) has been identified in P. lividus sea urchin embryo. It encodes a H3 histone protein showing the S.//.A.IG amino acid motif typical of the replication independent H3.3 variants but in a mRNA showing the 3' terminal stem-loop nucleotide sequence that is typical of the replication dependent variants. The gene is intronless, the corresponding short transcript is non-polyadenyl ated and its expression is replication dependent with a timing of late variant. The new H3 variant is expressed as a minor component with respect to a major replication dependent late H3 histone here identified by partial cDNA sequence. These results show that classification of histones in replication dependent and independent variants only on the basis of their amino acid sequences should be reconsidered.

Amino Acid Sequence↗