Sequencing the unsequenceable: expanded CGG-repeat alleles of the fragile X gene.
Genome Res
; 23(1): 121-8, 2013 Jan.
Article
em En
| MEDLINE
| ID: mdl-23064752
ABSTRACT
The human fragile X mental retardation 1 (FMR1) gene contains a (CGG)(n) trinucleotide repeat in its 5' untranslated region (5'UTR). Expansions of this repeat result in a number of clinical disorders with distinct molecular pathologies, including fragile X syndrome (FXS; full mutation range, greater than 200 CGG repeats) and fragile X-associated tremor/ataxia syndrome (FXTAS; premutation range, 55-200 repeats). Study of these diseases has been limited by an inability to sequence expanded CGG repeats, particularly in the full mutation range, with existing DNA sequencing technologies. Single-molecule, real-time (SMRT) sequencing provides an approach to sequencing that is fundamentally different from other "next-generation" sequencing platforms, and is well suited for long, repetitive DNA sequences. We report the first sequence data for expanded CGG-repeat FMR1 alleles in the full mutation range that reveal the confounding effects of CGG-repeat tracts on both cloning and PCR. A unique feature of SMRT sequencing is its ability to yield real-time information on the rates of nucleoside addition by the tethered DNA polymerase; for the CGG-repeat alleles, we find a strand-specific effect of CGG-repeat DNA on the interpulse distance. This kinetic signature reveals a novel aspect of the repeat element; namely, that the particular G bias within the CGG/CCG-repeat element influences polymerase activity in a manner that extends beyond simple nearest-neighbor effects. These observations provide a baseline for future kinetic studies of repeat elements, as well as for studies of epigenetic and other chemical modifications thereof.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Análise de Sequência de DNA
/
Alelos
/
Proteína do X Frágil da Deficiência Intelectual
Limite:
Humans
Idioma:
En
Revista:
Genome Res
Assunto da revista:
BIOLOGIA MOLECULAR
/
GENETICA
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Estados Unidos