Common haplotype of interleukin-6 gene is associated with chronic total occlusions of coronary arteries.

AIM: Genetic polymorphisms in genes coding for cytokines may predispose patients to coronary artery disease and chronic total occlusion (CTO) of coronary arteries. The aim of the study was to evaluate association of common genetic variations of interleukins (IL) with CTOs. METHODS: We reviewed coronary angiograms and evaluated presence of CTOs in 684 consecutive patients with no history of revascularization. The following genetic variations were analyzed: IL-1B +3954 C>T, IL-1B -511 C>T, IL-1RN VNTR and haplotypes of IL-6 encompassing IL-6 -596 G>A, IL-6 -572 G>C, IL-6 -373 AnTn and IL-6 -174 G>C polymorphisms. RESULTS: In 254 patients (37.1%) CTO of at least one artery was found. We observed nine IL-6 haplotypes, of which five were common (>1%) and one (GG9/12G, n=8) was not previously reported in literature. The most prevalent IL-6 haplotype (AG8/12C or Hap*1, 49.5%) correlated with CTOs, that were present in 31.5%, 36.5% and 44.5% of patients with none, one and two Hap*1, respectively (OR [95%CI] 1.252 [0.844-1.856] and 1.746 [1.104-2.762] for heterozygots and homozygots, respectively). In multivariate analysis this association became non-significant (OR [95%CI] 1.202 [0.805-1.796] and 1.529 [0.955-2.450]). In subgroup analysis Hap*1 was, however, associated with CTOs in the left anterior descending artery (p for trend 0.032) and the left circumflex artery (P=0.047), but not in the right coronary artery (p=0.799). In multivariate analysis CTOs of the left coronary arteries were associated only with total cholesterol (OR [95%CI] 1.170 [1.020-1.341]) and Hap*1 (OR [95%CI] 1.469 [0.914-2.361] and 1.970 [1.151-3.372] for heterozyogots and homozygots, respectively). CONCLUSION: Our study suggests that common IL-6 haplotype (AG8/12C or Hap*1) is associated with development of CTOs in left coronary arteries.

C-reactive protein levels and common polymorphisms of the interleukin-1 gene cluster and interleukin-6 gene in patients with coronary heart disease.

C-reactive protein (CRP) is an inflammatory marker associated with increased cardiovascular risk. Production of CRP is regulated by interleukin (IL)-1beta, IL-1 receptor antagonist and IL-6. In 160 patients with coronary heart disease (CHD) confirmed by angiography, we examined the relationship between CRP level and five polymorphisms in genes coding for these cytokines: IL-1B(-511), IL-1B(+3954), a variable number tandem repeat (VNTR) polymorphism in intron 2 of IL-1RN [IL-1RN(VNTR)], IL-6(-174) and IL-6(-572). CRP values were logarithmically normalized (log-CRP) for statistical calculations. In univariate analysis, carrier status for the IL-1B(+3954)T allele and IL-1RN(VNTR) allele 2 [IL-1RN(VNTR)*2] correlated with higher (P < 0.01) and lower (P < 0.05) log-CRP values, respectively. Among the potential confounding factors analysed, smoking, body mass index, total cholesterol (P < 0.05 for all) and diabetes (P = 0.056) were positively correlated with CRP level. After adjustment for non-genetic covariates, CRP levels remained significantly (P < 0.01) higher in carriers of IL-1B(+3954)T than in non-carriers: mean log-CRP (with 95% confidence interval) was 0.443 (0.311-0.574) for CT or TT genotypes compared with 0.240 (0.107-0.373) for the CC genotype, which corresponded to back-transformed CRP levels of 2.77 and 1.74 mg l(-1), respectively. Adjusted association was also significant for IL-1RN(VNTR)*2 (P < 0.01), with lower CRP levels in the presence of allele 2: the mean log-CRP value was 0.252 (0.115-0.388) for carriers and 0.421 (0.290-0.552) for non-carriers (CRP 1.79 and 2.64 mg l(-1), respectively). When alleles of both polymorphisms were entered into the model simultaneously, the association remained significant for IL-1B(+3954)T (P < 0.05), but not for IL-1RN(VNTR)*2. We conclude that IL-1B(+3954)T is associated with higher CRP levels in patients with CHD, and we found that this association was significant after adjustment for major risk factors. Our data also suggest a possible relationship of IL-1RN(VNTR)*2 with lower CRP levels in the same patients.

Forced retroevolution of an RNA bacteriophage.

The operator hairpin ahead of the replicase gene in RNA bacteriophage MS2 contains overlapping signals for binding the coat protein and ribosomes. Coat protein binding inhibits further translation of the gene and forms the first step in capsid formation. The hairpin sequence was partially randomized to assess the importance of this structure element for the bacteriophage and to monitor alternative solutions that would evolve on the passaging of mutant phages. The evolutionary reconstruction of the operator failed in the majority of mutants. Instead, a poor imitation developed containing only some of the recognition signals for the coat protein. Three mutants were of particular interest in that they contained double nonsense codons in the lysis reading frame that runs through the operator hairpin. The simultaneous reversion of two stop codons into sense codons has a very low probability of occurring. Therefore the phage solved the problem by deleting the nonsense signals and, in fact, the complete operator, except for the initiation codon of the replicase gene. Several revertants were isolated with activities ranging from 1% to 20% of wild type. The operator, long thought to be a critical regulator, now appears to be a dispensable element. In addition, the results indicate how RNA viruses can be forced to step back to an attenuated form.

Long-range translational coupling in single-stranded RNA bacteriophages: an evolutionary analysis.

In coliphage MS2 RNA a long-distance interaction (LDI) between an internal segment of the upstream coat gene and the start region of the replicase gene prevents initiation of replicase synthesis in the absence of coat gene translation. Elongating ribosomes break up the repressor LDI and thus activate the hidden initiation site. Expression studies on partial MS2 cDNA clones identified base pairing between 1427-1433 and 1738-1744, the so-called Min Jou (MJ) interaction, as the molecular basis for the long-range coupling mechanism. Here, we examine the biological significance of this interaction for the control of replicase gene translation. The LDI was disrupted by mutations in the 3'-side and the evolutionary adaptation was monitored upon phage passaging. Two categories of pseudorevertants emerged. The first type had restored the MJ interaction but not necessarily the native sequence. The pseudorevertants of the second type acquired a compensatory substitution some 80 nt downstream of the MJ interaction that stabilizes an adjacent LDI. In one examined case we confirmed that the second site mutations had restored coat-replicase translational coupling. Our results show the importance of translational control for fitness of the phage. They also reveal that the structure that buries the replicase start extends to structure elements bordering the MJ interaction.

Leeway and constraints in the forced evolution of a regulatory RNA helix.

The start of the coat protein gene of RNA phage MS2 adopts a well-defined hairpin structure of 12 bp (including one mismatch) in which the start codon occupies the loop position. An earlier expression study using partial MS2 cDNA clones had indicated that the stability of this hairpin is important for gene expression. For every -1.4 kcal/mol increase in stability a 10-fold reduction in coat protein was obtained. Destabilizations beyond the wild-type value did not affect expression. These results suggested that the hairpin was tuned in the sense that it has the highest stability still compatible with maximal ribosome loading. Employing an infectious MS2 cDNA clone, we have now tested the prediction that the delta G 0 of the coat protein initiator helix is set at a precise value. We have introduced stabilizing and destabilizing mutations into this hairpin in the intact phage and monitored their evolution to viable species. By compensatory mutations, both types of mutants quickly revert along various pathways to wild-type stability, but not to wild-type sequence. As a rule the second-site mutations do not change the encoded amino acids or the Shine-Dalgarno sequence. The return of too strong hairpins to wild-type stability can be understood from the need to produce adequate supplies of coat protein. The return of unstable hairpins to wild-type stability is not self-evident and is presently not understood. The revertants provide an evolutionary landscape of slightly suboptimal phages, that were stable at least for the duration of the experiment (approximately 20 infection cycles).(ABSTRACT TRUNCATED AT 250 WORDS)