RESUMO
BACKGROUND AND PURPOSE: Although the Mexican population has a high predisposition to dyslipidemias and premature coronary artery disease, this population is underinvestigated for the genetic factors conferring the high susceptibility. This study attempted to determine these genetic factors. METHODS AND RESULTS: First, we investigated apolipoprotein B (apoB) levels in Mexican extended families with familial combined hyperlipidemia using a two-step testing strategy. In the screening step, we screened 5721 single-nucleotide polymorphisms (SNPs) for linkage signals with apoB. In the test step, we analyzed the 130 SNPs residing in regions of suggestive linkage signals for association with apoB. We identified significant associations with two SNPs (ie, rs1424032 [P=6.07x10(-6)] and rs1349411 [P=2.72x10(-4)]) that surpassed the significance level for the number of tests performed in the test step (P<3.84x10(-4)). Second, these SNPs were tested for replication in Mexican hyperlipidemic case-control samples. The same risk alleles as in the families with familial combined hyperlipidemia were significantly associated (P<0.05) with apoB in the case-control samples. The rs1349411 resides near the apoB messenger RNA editing enzyme (APOBEC1) involved in the processing of APOB messenger RNA in the small intestine. The rs1424032 resides in a highly conserved noncoding region predicted to function as a regulatory element. CONCLUSIONS: We identified two novel variants, rs1349411 and rs1424032, for serum apoB levels in Mexicans.
Assuntos
Indígena Americano ou Nativo do Alasca/genética , Apolipoproteínas B/genética , Citidina Desaminase/genética , Hiperlipidemia Familiar Combinada/genética , Hiperlipidemias/genética , Polimorfismo de Nucleotídeo Único , Desaminase APOBEC-1 , Adulto , Apolipoproteínas B/metabolismo , Estudos de Casos e Controles , Citidina Desaminase/metabolismo , Feminino , Frequência do Gene , Ligação Genética , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Humanos , Hiperlipidemia Familiar Combinada/sangue , Hiperlipidemia Familiar Combinada/etnologia , Hiperlipidemias/sangue , Hiperlipidemias/etnologia , Masculino , México/epidemiologia , Análise de Sequência com Séries de Oligonucleotídeos , Linhagem , Fenótipo , RNA Mensageiro/metabolismo , Fatores de RiscoRESUMO
Apobec1 edits the ApoB mRNA by deaminating nucleotide C(6666), which results in a codon change from Glutamate to stop, and subsequent expression of a truncated protein. Apobec1 is regulated by ACF (Apobec1 complementation factor) and hnRNPQ, which contains an N-terminal "acidic domain" (AcD) of unknown function, three RNA recognition motifs, and an Arg/Gly-rich region. Here, we modeled the structure of AcD using the bacterial protein Barstar as a template. Furthermore, we demonstrated by in vitro pull-down assays that 6xHis-AcD alone is able to interact with GST-Apobec1. Finally, we performed in silico phosphorylation of AcD and molecular dynamics studies, which indicate conformational changes in the phosphorylated form. The results of the latter studies were confirmed by in vitro phosphorylation of 6xHis-AcD by protein kinase C, mass spectrometry, and spectroscopic analyses. Our data suggest hnRNPQ interactions via its AcD with Apobec1 and that this interaction is regulated by the AcD phosphorylation.