Nα-acetyltransferase NatA is involved in ribosome synthesis in Saccharomyces cerevisiae.

Ebp2 has an essential role in the biogenesis of 60S ribosomal subunits. Synthetic-sick alleles with the ebp2-14 mutation were screened. The mutations were localized to the ARD1 and NAT1 genes, which encode the catalytic subunit and the auxiliary subunit of N(α)-acetyltransferase NatA respectively. Polysome analyses revealed that ard1Δ and nat1Δ caused a synergistic defect with ebp2-14 in the assembly of 60S ribosomal subunits. To identify the proteins that functionally interact with NatA, we designed mutants in which the second amino acid was substituted for proline in Ebp2 and functionally related proteins: Brx1, a partner of Ebp2 in ribosome biogenesis, and the ribosomal protein L36a/b, overexpression of which suppresses a growth defect in ebp2-14. Among these, only brx1-S2P exhibited a synthetic defect with ebp2-14. These results suggest that optimal NatA function is important to the cooperative function of Brx1 with Ebp2 in 60S ribosomal subunit biogenesis.

Ebp2 and Brx1 function cooperatively in 60S ribosomal subunit assembly in Saccharomyces cerevisiae.

The yeast protein Ebp2 is required for early steps in production of 60S ribosomal subunits. To search for cofactors with which Ebp2 functions, or substrates on which it acts, we screened for mutants that were synthetically lethal (sl) with the ebp2-14 mutation. Four different mutant alleles of the 60S ribosomal subunit assembly factor Brx1 were found. To investigate defects of the double mutant, we constructed strains conditional for the ebp2-14 brx1- synthetic lethal phenotype. These ebp2-14 brx1 mutants were defective in processing of 27S pre-rRNA and production of 60S subunits, under conditions where each single mutant was not. Ebp2 and Brx1 exhibit a strong two-hybrid interaction, which is eliminated by some combinations of brx1 and ebp2 mutations. In one such mutant, Ebp2 and Brx1 can still associate with pre-ribosomes, but subunit maturation is perturbed. Depletion of either Ebp2 or Brx1 revealed that Brx1 requires Ebp2 for its stable association with pre-ribosomes, but Ebp2 does not depend on the presence of Brx1 to enter pre-ribosomes. These results suggest that assembly of 60S ribosomal subunits requires cooperation of Ebp2 with Brx1, together with other molecules present in pre-ribosomes, potentially including several found in assembly subcomplexes with Brx1 and Ebp2.

An adult with atopic dermatitis and repeated short-term fasting.

It has been reported that nutritional stress, such as short-term fasting and long-term energy restriction, has a suppressive effect on allergic dermatitis in experimental animals. Furthermore, clinical study has demonstrated a positive association between weight loss by low-energy diet and improvement in patients with atopic dermatitis. In this report, a 23-year-old female with atopic dermatitis received a treatment of repeated short-term fasting. 24-hour fasting was conducted once a week for a period of 20 weeks. On the fasting day, the amount of energy intake was 200 kcal. No medication was administered during the trial period. Clinical symptoms were evaluated using the Scoring Atopic Dermatitis index, and IgE, lactase dehydrogenase-5, and number of eosinophils were measured. At the end of the trial, body weight was reduced and clinical symptoms improved, whereas no improvements in laboratory findings were shown. For sufficient evidence of the effects of fasting, additional controlled study is needed.