RESUMO
Using entire modern and ancient mitochondrial genomes of Adélie penguins (Pygoscelis adeliae) that are up to 44000 years old, we show that the rates of evolution of the mitochondrial genome are two to six times greater than those estimated from phylogenetic comparisons. Although the rate of evolution at constrained sites, including nonsynonymous positions and RNAs, varies more than twofold with time (between shallow and deep nodes), the rate of evolution at synonymous sites remains the same. The time-independent neutral evolutionary rates reported here would be useful for the study of recent evolutionary events.
Assuntos
Evolução Molecular , Genoma Mitocondrial/genética , Spheniscidae/genética , Animais , DNA Mitocondrial/química , Variação Genética , Genética Populacional , HumanosRESUMO
The translation of the unspliced and partially spliced viral mRNAs that encode the late, structural proteins of HIV-1 depends on the viral-protein Rev. Oligomeric binding of Rev to the Rev response element (RRE) in these mRNAs promotes their export from the nucleus and thus controls their expression. Here, we compared the effects of hydrophobic to hydrophilic mutations within the oligomerization domain of Rev using assays for oligomeric RNA binding, protein structure, and export from the nucleus. Oligomeric RNA binding alone does not correlate well with RNA transport activity in the subset of mutants. However, protein structure as judged by CD spectroscopy does correlate well with Rev function. The oligomeric assembly of Rev-L18T is impaired but exhibits minor defects in structure and retains a basal level of activity in vivo. The prevalence of L18T in infected individuals suggests a positive selection mechanism for L18T modulation of Rev activity that may delay the onset of AIDS.
Assuntos
RNA Viral/química , Produtos do Gene rev do Vírus da Imunodeficiência Humana/química , Sequência de Aminoácidos , Sítios de Ligação , Genes Reporter , Variação Genética , Células HeLa , Humanos , Dados de Sequência Molecular , Mutação , Mutação Puntual , Ligação Proteica , Conformação Proteica , Estrutura Terciária de Proteína , Transporte de RNA , RNA Mensageiro/química , RNA Mensageiro/metabolismo , RNA Viral/metabolismo , Alinhamento de Sequência , Produtos do Gene rev do Vírus da Imunodeficiência Humana/genética , Produtos do Gene rev do Vírus da Imunodeficiência Humana/metabolismoRESUMO
The retinoid-related orphan receptor alpha (RORalpha) belongs to the nuclear receptor superfamily and comprises four isoforms generated by different promotor usage and alternative splicing. To better understand its function, the subcellular distribution of RORalpha was investigated. We could show that subcellular distribution of RORalpha is cell line and isoform-dependent. Isoform specific differences were mediated by the A/B domains which with the exception of RORalpha1 contain a signal that mediates cytoplasmic localization. The lack of this signal in RORalpha1 results in a complete nuclear localization and prevents cell membrane association observed for RORalpha2, 3, and 4. The region responsible for membrane association was identified as the C-terminal alpha-helix 12. Furthermore, the hinge region/ligand binding domain mediates nuclear localization. Our results show that isoform specific activity of RORalpha is not only regulated by different expression and DNA binding affinities but also by different subcellular distribution. Different access to the nucleus reveals an important mechanism regulating the activity of this constitutively active nuclear receptor.
