Snaevar Sigurdsson | PubMed Health

PubMed2002

Multiplex SNP genotyping in pooled DNA samples by a four-colour microarray system.

We selected 125 candidate single nucleotide polymorphisms (SNPs) in genes belonging to the human type 1 interferon (IFN) gene family and the genes coding for proteins in the main type 1 IFN signalling pathway by screening databases and by in silico comparison of DNA sequences. Using quantitative analysis of pooled DNA samples by solid-phase mini-sequencing, we found that only 20% of the candidate SNPs were polymorphic in the Finnish and Swedish populations. To allow more effective validation of candidate SNPs, we developed a four-colour microarray-based mini-sequencing assay for multiplex, quantitative allele frequency determination in pooled DNA samples. We used cyclic mini-sequencing reactions with primers carrying 5'-tag sequences, followed by capture of the products on microarrays by hybridisation to complementary tag oligonucleotides. Standard curves prepared from mixtures of known amounts of SNP alleles demonstrate the applicability of the system to quantitative analysis, and showed that for about half of the tested SNPs the limit of detection for the minority allele was below 5%. The microarray-based genotyping system established here is universally applicable for genotyping and quantification of any SNP, and the validated system for SNPs in type 1 IFN-related genes should find many applications in genetic studies of this important immunoregulatory pathway.

Cluster Analysis↗

PubMed2002

Structural basis for the inhibitory efficacy of efavirenz (DMP-266), MSC194 and PNU142721 towards the HIV-1 RT K103N mutant.

The K103N substitution is a frequently observed HIV-1 RT mutation in patients who do not respond to combination-therapy. The drugs Efavirenz, MSC194 and PNU142721 belong to the recent generation of NNRTIs characterized by an improved resistance profile to the most common single point mutations within HIV-1 RT, including the K103N mutation. In the present study we present structural observations from Efavirenz in complex with wild-type protein and the K103N mutant and PNU142721 and MSC194 in complex with the K103N mutant. The structures unanimously indicate that the K103N substitution induces only minor positional adjustments of the three inhibitors and the residues lining the binding pocket. Thus, compared to the corresponding wild-type structures, these inhibitors bind to the mutant in a conservative mode rather than through major rearrangements. The structures implicate that the reduced inhibitory efficacy should be attributed to the changes in the chemical environment in the vicinity of the substituted N103 residue. This is supported by changes in hydrophobic and electrostatic interactions to the inhibitors between wild-type and K103N mutant complexes. These potent inhibitors accommodate to the K103N mutation by forming new interactions to the N103 side chain. Our results are consistent with the proposal by Hsiou et al. [Hsiou, Y., Ding, J., Das, K., Clark, A.D. Jr, Boyer, P.L., Lewi, P., Janssen, P.A., Kleim, J.P., Rosner, M., Hughes, S.H. & Arnold, E. (2001) J. Mol. Biol. 309, 437-445] that inhibitors with good activity against the K103N mutant would be expected to have favorable interactions with the mutant asparagines side chain, thereby compensating for resistance caused by stabilization of the mutant enzyme due to a hydrogen-bond network involving the N103 and Y188 side chains.

Acetophenones↗