RET codon 609 mutations: a contribution for better clinical managing

Medullary thyroid carcinoma currently accounts for 5-8% of all thyroid cancers. The clinical course of this disease varies from extremely indolent tumors that can go unchanged for years to an extremely aggressive variant that is associated with a high mortality rate. As many as 75% of all medullary thyroid carcinomas are sporadic, with an average age at presentation reported as 60 years, and the remaining 25% are hereditary with an earlier age of presentation, ranging from 20 to 40 years. Germline RET proto-oncogene mutations are the genetic causes of multiple endocrine neoplasia type 2 and a strong genotype-phenotype correlation exists, particularly between a specific RET codon mutation and the (a) age-related onset and (b) thyroid tumor progression, from C-cell hyperplasia to medullary thyroid carcinoma and, ultimately, to nodal metastases. RET mutations predispose an individual to the development of medullary thyroid carcinomas and can also influence the individual response to RET protein receptor-targeted therapies. RET codon 609point mutations are rare genetic events belonging to the intermediate risk category for the onset of medullary thyroid carcinoma. A large genealogy resulting in a less aggressive form of medullary thyroid carcinoma is associated with the high penetrance of pheochromocytoma and has been reported in the literature. In this short review article, we comment on our previous report of a large multiple endocrine neoplasia type 2A kindred with the same Cys609Ser germline RET mutation in which, conversely, the syndrome was characterized by a slightly aggressive, highly penetrant form of medullary thyroid carcinoma that was associated with low penetrance of pheochromocytoma and primary hyperparathyroidism.

Permanent neonatal diabetes due to KCNJ11 gene mutation.

Permanent neonatal diabetes mellitus (PNDM) is characterized by the onset of diabetes within the first six months of life and insulin dependence life long. It has been recently discovered that mutation in KCNJ11 gene encoding Kir6.2, the pore forming subunit of ATP sensitive potassium channel (K ATP) is the most common cause and such patients may respond better to oral sulphonylurea drugs than insulin. Here is a rare case of permanent neonatal diabetes due to R20IC mutation in KCNJ11 gene.

Mechanism of DNA-binding loss upon single-point mutation in p53.

Over 50% of all human cancers involve p53 mutations,which occur mostly in the sequence-specific DNA-binding central domain (p53c), yielding little/non-detectable af?nity to the DNA consensus site.Despite our current understanding of protein-DNA recognition,the mechanism(s) underlying the loss in protein-DNA binding afnity/ specificity upon single-point mutation are not well understood. Our goal is to identify the common factors governing the DNA-binding loss of p53c upon substitution of Arg 273 to His or Cys,which are abundant in human tumours. By computing the free energies of wild-type and mutant p53c binding to DNA and decomposing them into contributions from individual residues, the DNA-binding loss upon charge/noncharge -conserving mutation of Arg 273 was attributed not only to the loss of DNA phosphate contacts, but also to longer-range structural changes caused by the loss of the Asp 281 salt-bridge. The results herein and in previous works suggest that Asp 281 plays a critical role in the sequence-specific DNA-binding function of p53c by (i)orienting Arg 273 and Arg 280 in an optimal position to interact with the phosphate and base groups of the consensus DNA, respectively, and (ii) helping to maintain the proper DNA-binding protein conformation.

Evidence that the fully assembled capsid of Leishmania RNA virus 1-4 possesses catalytically active endoribonuclease activity

In this study, Leishmania RNA virus 1-4 (LRV1-4) particles purified from host Leishmania guyanensis promastigotes were examined for capsid endoribonuclease. Temperature optimum for the endoribonulease activity was found to be at 37degrees C to 42degrees C and the activity was specifically inhibited by the aminoglycoside antibiotics, neomycin, kanamycin, and hygromycin and by 100 mM levels of NaCl or KCl. To determine the catalytic domain of the capsid endoribonuclease activity, three point-mutation at cysteine residues at C47S (P1), C128/ 133S (P2), and C194R (P3) were prepared and each gene was constructed into baculoviruses and expressed in Sf9 insect cells. LRV1-4 capsid N- terminus (N2 and N3) and C-terminus (C1 and C2) deletion mutants (Cadd et al., 1994) were also examined by in vitro RNA cleavage assay. The results showed that the capsid mutants; C1, C2, N3, P1, and P2 were capable of forming proper virus-like particles (VLPs) and they all possessed the specific endoribonuclease activity. However, two assembly-defective capsid mutants, N2 (N- terminus 24-amino acids deletion) and P3 mutants, did not retain the specific endoribonuclease activity. Taken together, the results suggest that at least 24 amino acids from the N-terminal region and C194 residue in LRV1-4 capsid protein are functionally important for LRV1-4 viral assembly and the capsid endoribonuclease activity may be dependent upon the properly assembled LRV1-4 virus particles.

Gold compound auranofin inhibits I kappaB kinase (IKK) by modifying Cys-179 of IKK beta subunit

Antirheumatic gold compounds have been shown to inhibit NF-kB activation by blocking IkB kinase (IKK) activity. To examine the possible inhibitory mechanism of gold compounds, we expressed wild type and mutant forms of IKk alpha and beta subunits in COS-7 cells and determined the effect of gold on the activity of these enzymes both in vivo and in vitro. Substitution of Cys-179 of IKK beta with alanine (C179A) rendered the enzyme to become resistant to inhibition by a gold compound auranofin, however, similar protective effect was not observed with an equivalent level of IKK alpha (C178A) mutant expressed in the cells. Auranofin inhibited constitutively active IKK alpha and beta and variants; IKK alpha (S176E, S180E) or IKK beta (S177E, S181E), suggesting that gold directly cause inhibition of activated enzyme. The different inhibitory effect of auranofin on IKK alpha (C178A) and IKK beta (C179A) mutants indicates that gold could inhibit the two subunits of IKK in a different mode, and the inhibition of NF- kB and IKK activation induced by inflammatory signals in gold-treated cells appears through its interaction with Cys-179 of IKK beta.