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Site-specific recombination requires conserved DNA sequences specific to each system, and system-specific proteins that recognize specific DNA sequences. The site-specific recombinases seem to fall into at least two families, based on their protein structure and chemistry of strand breakage. One of these is the resolvase-invertase family, members of which seem to form a serine-phosphate linkage with DNA. Members of the other family, called the integrase family, contain a conserved tyrosine residue that forms a covalent linkage with the 3'-phosphate of DNA at the site of recombination. Structural comparison of integrases shows that these proteins share a highly conserved 40-residue motif. V-(D)-J recombination of the immunoglobulin gene requires conserved recombination signal sequences (RS) of a heptamer CACTGTG and a T-rich nonamer GGTTTTTGT, which are separated by a spacer sequence of either 12 or 23 bases We have recently purified, almost to homogeneity, a protein that specifically binds to the immunoglobulin J kappa RS containing the 23-base-pair spacer sequence. By synthesizing probes on the basis of partial amino-acid sequences of the purified protein, we have now isolated and characterized the complementary DNA of this protein. The amino-acid sequence deduced from the cDNA sequence reveals that the J kappa RS-binding protein has a sequence similar to the 40-residue motif of integrases of phages, bacteria and yeast, indicating that this protein could be involved in V-(D)-J recombination as a recombinase.

Highlights Close relationship is found between low serum zinc and severe states of COVID-19. Hypozincemia critically contributes to aggravation of COVID-19. Serum zinc level can be predictive factor for critical illness of COVID-19. We would recommend oral medication of zinc salts to patients with COVID-19. Abstract Objectives Because most severely ill patients with COVID-19 in our hospital showed zinc deficiency, we aimed to examine the relationship between the patient’s serum zinc level and severe cases of COVID-19. Methods Serum zinc <70 µg/dL was defined as the criterion for hypozincemia, and patients continuously with serum zinc <70 µg/dL were classified in the hypozincemia cohort. To evaluate whether hypozincemia could be a predictive factor for critical illness of COVID-19, we performed the multivariate analysis by employing logistic regression analysis. Results Prolonged hypozincemia was found to be a risk factor for a severe case of COVID-19. In evaluating the relationship between the serum zinc level and severity of patients with COVID-19 by multivariate logistic regression analysis, critical illness can be predicted through the sensitivity and false specificity of an ROC curve with an error rate of 10.3% and AUC of 94.2% by only two factors: serum zinc value ( P = 0.020) and LDH value ( P = 0.026). Conclusions Proper management of the prediction results in this study can contribute to the establishment and maintenance of a safe medical system, taking the arrival of the second wave and spread of COVID-19 in the future into consideration.

Fructose-1,6-bisphosphatase (FBPase) deficiency is an autosomal recessive inherited disorder and may cause sudden unexpected infant death. We reported the first case of molecular diagnosis of FBPase deficiency, using cultured monocytes as a source for FBPase mRNA. In the present study, we confirmed the presence of the same genetic mutation in this patient by amplifying genomic DNA. Molecular analysis was also performed to diagnose another 12 Japanese patients with FBPase deficiency. Four mutations responsible for FBPase deficiency were identified in 10 patients from 8 unrelated families among a total of 13 patients from 11 unrelated families; no mutation was found in the remaining 3 patients from 3 unrelated families. The identified mutations included the mutation reported earlier, with an insertion of one G residue at base 961 in exon 7 (960/961insG) (10 alleles, including 2 alleles in the Japanese family from our previous report [46% of the 22 mutant alleles]), and three novel mutations--a G-->A transition at base 490 in exon 4 (G164S) (3 alleles [14%]), a C-->A transversion at base 530 in exon 4 (A177D) (1 allele [4%]), and a G-->T transversion at base 88 in exon 1 (E30X) (2 alleles [9%]). FBPase proteins with G164S or A177D mutations were enzymatically inactive when purified from E. coli. Another new mutation, a T-->C transition at base 974 in exon 7 (V325A), was found in the same allele with the G164S mutation in one family (one allele) but was not responsible for FBPase deficiency. Our results indicate that the insertion of one G residue at base 961 was associated with a preferential disease-causing alternation in 13 Japanese patients. Our results also indicate accurate carrier detection in eight families (73%) of 11 Japanese patients with FBPase deficiency, in whom mutations in both alleles were identified.

We have investigated whether J kappa recombination signal sequence (RS) binding protein (RBP-J kappa) has any partial catalytic activities involved in the VDJ recombination reaction, such as cleavage, ligation, and bending of DNA. Murine RBP-J kappa protein purified by J kappa-RS affinity chromatography did not show DNA cleavage activities but contained a strong DNA ligase activity. To obtain a large amount of purified RBP-J kappa protein, recombinant RBP-J kappa was synthesized in Escherichia coli as a fusion protein and also in silkworm cells. Although recombinant RBP-J kappa produced in silkworm cells could bind J kappa-RS, it failed to show either ligase or DNA bending activity. Since the DNA affinity-purified RBP-J kappa has the ligase activity, the RBP-J kappa protein may form a complex with a ligase in vivo. We have raised monoclonal antibodies against the RBP-J kappa fusion protein which was synthesized in E. coli and unable to bind J kappa-RS. Using the anti-RBP-J kappa monoclonal antibody we have shown that the RBP-J kappa protein is expressed ubiquitously in mammalian tissues. The ubiquitous expression of the RBP-J kappa protein is consistent with the hypothesis that the RBP-J kappa protein may have dual function [Furukawa et al. (1991) J. Biol. Chem. 266, 23334-23340].