RNA Binding of T-cell Intracellular Antigen-1 (TIA-1) C-terminal RNA Recognition Motif Is Modified by pH Conditions

T-cell intracellular antigen-1 (TIA-1) is a DNA/RNA-binding protein that regulates critical events in cell physiology by the regulation of pre-mRNA splicing and mRNA translation. TIA-1 is composed of three RNA recognition motifs (RRMs) and a glutamine-rich domain and binds to uridine-rich RNA sequences through its C-terminal RRM2 and RRM3 domains. Here, we show that RNA binding mediated by either isolated RRM3 or the RRM23 construct is controlled by slight environmental pH changes due to the protonation/deprotonation of TIA-1 RRM3 histidine residues. The auxiliary role of the C-terminal RRM3 domain in TIA-1 RNA recognition is poorly understood, and this work provides insight into its binding mechanisms.     

UGT1A1 sequence variants associated with risk of adult hyperbilirubinemia: A quantitative analysis

Backgrounds and Aims

UDP-glucuronosyltransferase 1 A1 (UGT1A1) is an enzyme that transforms small lipophilic molecules into water-soluble and excretable metabolites. UGT1A1 polymorphisms contribute to hyperbilirubinemia. This study quantitatively associated UGT1A1 variants in patients with hyperbilirubinemia and healthy subjects.

Methods

A total of 104 individuals with hyperbilirubinemia and 105 healthy controls were enrolled for genotyping and DNA sequencing UGT1A1 sequence variants, including the Phenobarbital Response enhancer module (PBREM) region, the promoter region (TATA box), and the 5 exons for quantitative association with hyperbilirubinemia.

Results

Eleven UGT1A1 variants were revealed in the case and control subjects, four of which were novel coding variants. A variant of PBREM (UGT1A1*60) was found in 47.6% of the patients, a TA repeat motif in the 5-primer promoter region [A(TA)₇TAA,UGT1A1*28] was found in 27.9% of the patients, and p.G71R (UGT1A1*6) was in 33.2% of the patients. For the healthy controls, the frequency of UGT1A1*60, UGT1A1*28 and UGT1A1*6 was 26.7%, 9.0% and 15.7%, respectively. Homozygous UGT1A1*28 and homozygous UGT1A1*6 were significantly associated with the risk of adult hyperbilirubinemia, with an odds ratio (OR) of 17.79 (95% CIs, 2.11–133.61) and 14.93 (95% CIs, 1.83–121.88), respectively. Quantitative analysis showed that sense mutation (including UGT1A1*6) and UGT1A1*28/*28, but not UGT1A1*60/*60 or UGT1A1*1/*28, was associated with increased serum total bilirubin (TB) levels. High linkage disequilibrium occurred between UGT1A1*60 and UGT1A1*28 (D′ = 0.964, r² = 0.345).

Conclusions

This study identified four novel UGT1A1 coding variants, some of which were associated with increased serum TB levels. A quantitative approach to evaluate adult hyperbilirubinemia provides a more vigorous framework for better understanding of adult hyperbilirubinemia genetics.     

A Shrimp C-type Lectin Inhibits Proliferation of the Hemolymph Microbiota by Maintaining the Expression of Antimicrobial Peptides

Some aquatic invertebrates such as shrimp contain low albeit stable numbers of bacteria in the circulating hemolymph. The proliferation of this hemolymph microbiota in such a nutrient-rich environment is tightly controlled in healthy animals, but the mechanisms responsible had remained elusive. In the present study, we report a C-type lectin (MjHeCL) from the kuruma shrimp (Marsupenaeus japonicus) that participates in restraining the hemolymph microbiota. Although the expression of MjHeCL did not seem to be modulated by bacterial challenge, the down-regulation of its expression by RNA interference led to proliferation of the hemolymph microbiota, ultimately resulting in shrimp death. This phenotype was rescued by the injection of recombinant MjHeCL, which restored the healthy status of the knockdown shrimp. A mechanistic analysis revealed that MjHeCL inhibited bacterial proliferation by modulating the expression of antimicrobial peptides. The key function of MjHeCL in the shrimp immune homeostasis might be related to its broader recognition spectrum of the hemolymph microbiota components than other lectins. Our study demonstrates the role of MjHeCL in maintaining the healthy status of shrimp and provides new insight into the biological significance of C-type lectins, a diversified and abundant lectin family in invertebrate species.     

寄生植物种子萌发特异性及其与寄主的识别机制

寄生植物广泛分布于不同的生态环境中,并具有不同的生育习性及与寄主识别特性.本文阐述了根寄生植物列当属和独脚金属种子萌发的特异性,以及目前已发现的寄生植物种子萌发的信号物质,并就不同萌发信号物质、植物激素、真菌代谢物在寄生植物种子识别寄主中的作用以及寄生植物种子预培养阶段的呼吸作用特性与萌发信号物质的活化机理等做了综述.探讨了各种列当不同分化类型的愈伤组织诱导、离体无菌侵染新系统及其在寄生植物与寄主互作识别研究中的应用,提出了寄生植物与寄主识别机理研究中存在的问题并对研究前景进行了展望.     

The energetic basis underpinning T-cell receptor recognition of a super-bulged peptide bound to a major histocompatibility complex class I molecule

Although the major histocompatibility complex class I (MHC-I) molecules typically bind short peptide (p) fragments (8-10 amino acids in length), longer, "bulged" peptides are often be presented by MHC-I. Such bulged pMHC-I complexes represent challenges for T-cell receptor (TCR) ligation, although the general principles underscoring the interaction between TCRs and bulged pMHC-I complexes are unclear. To address this, we have explored the energetic basis of how an immunodominant TCR (termed SB27) binds to a 13-amino acid viral peptide (LPEPLPQGQLTAY) complexed to human leukocyte antigen (HLA) B*3508. Using the crystal structure of the SB27 TCR-HLA B*3508(LPEP) complex as a guide, we undertook a comprehensive alanine-scanning mutagenesis approach at the TCR-pMHC-I interface and examined the effect of the mutations by biophysical (affinity measurements) and cellular approaches (tetramer staining). Although the structural footprint on HLA B*3508 was small, the energetic footprint was even smaller in that only two HLA B*3508 residues were critical for the TCR interaction. Instead, the energetic basis of this TCR-pMHC-I interaction was attributed to peptide-mediated interactions in which the complementarity determining region 3α and germline-encoded complementarity determining region 1β loops of the SB27 TCR played the principal role. Our findings highlight the peptide-centricity of TCR ligation toward a bulged pMHC-I complex.