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Gene Evolution - Fast or Slow?02:05

Gene Evolution - Fast or Slow?

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
In contrast, regions which code...
Non-LTR Retrotransposons03:18

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As the name suggests, non-LTR retrotransposons lack the long terminal repeats characteristic of the LTR retrotransposons. Additionally, both LTR and non-LTR retrotransposons use distinct mechanisms of mobilization. Non-LTR retrotransposons are further divided into two classes - Long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), both of which occur abundantly in most mammals, including humans. Some of the active non-LTR retrotransposons in humans are L1...
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Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. The multisubunit structure of the bacterial RNAP helps the enzyme to maintain catalytic function, facilitate assembly, interact with DNA and RNA, and self-regulate its activity.
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Bacterial Transcription01:53

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RNA polymerase (RNAP) carries out DNA-dependent RNA synthesis in both bacteria and eukaryotes. Bacteria do not have a membrane-bound nucleus. So, transcription and translation occur simultaneously, on the same DNA template.
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Gene Evolution - Fast or Slow?02:05

Gene Evolution - Fast or Slow?

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
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Pre-mRNA Processing: Modification of pre-mRNA Ends01:35

Pre-mRNA Processing: Modification of pre-mRNA Ends

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Assessment of DNA Contamination in RNA Samples Based on Ribosomal DNA
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Identificación del Rap1 humano: implicaciones para la evolución de los telómeros.

B Li1, S Oestreich, T de Lange

  • 1The Rockefeller University, New York, New York 10021, USA.

Cell
|June 13, 2000
PubMed
Resumen

Los investigadores identificaron el Rap1 humano (hRap1) como una proteína telomérica ortológica de la levadura Rap1. Este hallazgo ayuda a explicar la ausencia de algunas proteínas teloméricas de mamíferos en la levadura en ciernes y sugiere la conservación evolutiva de los componentes de los telómeros.

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Área de la Ciencia:

  • Biología Molecular Biología Molecular
  • Genética La genética.
  • Biología celular Biología celular.

Sus antecedentes:

  • Los telómeros de los mamíferos poseen proteínas como TRF1, TRF2, tanquirasas y TIN2, que carecen de contrapartes claras en la levadura en ciernes.
  • Las relaciones evolutivas de las proteínas teloméricas en diferentes especies de levaduras y mamíferos siguen siendo incompletamente entendidas.

Objetivo del estudio:

  • Para identificar y caracterizar ortólogos de proteínas teloméricas de levadura en mamíferos y levadura de fisión.
  • Para aclarar la historia evolutiva y la conservación de los complejos de proteínas teloméricas.

Principales métodos:

  • Análisis de homología de secuencias para identificar motivos conservados entre humanos y levaduras Rap1.
  • Estudios de localización de telómeros utilizando técnicas de imágenes celulares.
  • Análisis funcionales para evaluar el impacto en el mantenimiento de la longitud de los telómeros.

Principales resultados:

  • Una proteína humana, hRap1, fue identificada como un ortólogo de la proteína telomérica de la levadura en ciernes scRap1p, compartiendo motivos de secuencia conservados.
  • hRap1 se localiza en los telómeros e influye en la longitud de los telómeros, pero a diferencia de scRap1p, es reclutado por TRF2.
  • La proteína Taz1 de la levadura de fisión fue identificada como un ortólogo de TRF, lo que indica la conservación de TRF.

Conclusiones:

  • Los hallazgos sugieren que los telómeros ancestrales contenían tanto proteínas similares a TRF como Rap1, similares a los vertebrados.
  • La levadura en brote puede haber retenido Rap1 en los telómeros mientras pierde el componente TRF, potencialmente relacionado con cambios en las secuencias de repetición teloméricas.