A critical context-dependent role for E boxes in the targeting of somatic hypermutation.
J Immunol
; 191(4): 1556-66, 2013 Aug 15.
Article
en En
| MEDLINE
| ID: mdl-23836058
ABSTRACT
Secondary B cell repertoire diversification occurs by somatic hypermutation (SHM) in germinal centers following Ag stimulation. In SHM, activation-induced cytidine deaminase mutates the V region of the Ig genes to increase the affinity of Abs. Although SHM acts primarily at Ig loci, low levels of off-target mutation can result in oncogenic DNA damage, illustrating the importance of understanding SHM targeting mechanisms. A candidate targeting motif is the E box, a short DNA sequence (CANNTG) found abundantly in the genome and in many SHM target genes. Using a reporter assay in chicken DT40 B cells, we previously identified a 1928-bp portion of the chicken IgL locus capable of supporting robust SHM. In this article, we demonstrate that mutation of all 20 E boxes in this fragment reduces SHM targeting activity by 90%, and that mutation of subsets of E boxes reveals a functional hierarchy in which E boxes within "core" targeting regions are of greatest importance. Strikingly, when the sequence and spacing of the 20 E boxes are preserved but surrounding sequences are altered, SHM targeting activity is eliminated. Hence, although E boxes are vital SHM targeting elements, their function is completely dependent on their surrounding sequence context. These results suggest an intimate cooperation between E boxes and other sequence motifs in SHM targeting to Ig loci and perhaps also in restricting mistargeting to certain non-Ig loci.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Linfocitos B
/
Hipermutación Somática de Inmunoglobulina
/
Elementos E-Box
Tipo de estudio:
Prognostic_studies
Límite:
Animals
Idioma:
En
Revista:
J Immunol
Año:
2013
Tipo del documento:
Article
País de afiliación:
Estados Unidos