Rcl1 protein, a novel nuclease for 18 S ribosomal RNA production.

In all forms of life, rRNAs for the small and large ribosomal subunit are co-transcribed as a single transcript. Although this ensures the equimolar production of rRNAs, it requires the endonucleolytic separation of pre-rRNAs to initiate rRNA production. In yeast, processing of the primary transcript encoding 18 S, 5.8 S, and 25 S rRNAs has been studied extensively. Nevertheless, most nucleases remain to be identified. Here, we show that Rcl1, conserved in all eukaryotes, cleaves pre-rRNA at so-called site A(2), a co-transcriptional cleavage step that separates rRNAs destined for the small and large subunit. Recombinant Rcl1 cleaves pre-rRNA mimics at site A(2) in a reaction that is sensitive to nearby RNA mutations that inhibit cleavage in vivo. Furthermore, mutations in Rcl1 disrupt rRNA processing at site A(2) in vivo and in vitro. Together, these results demonstrate that the role of Rcl1 in eukaryotic pre-rRNA processing is identical to that of RNase III in bacteria: to co-transcriptionally separate the pre-rRNAs destined for the small and large subunit. Furthermore, because Rcl1 has no homology to other known endonucleases, these data also establish a novel class of nucleases.

Who needs grief counseling? A report from the Scott & White Grief Study.

Cluster analysis was performed on a diverse group of 69 non-clinical grievers whose loved ones died between 12-40 months prior to the study. Based on psychometric measures of both bereavement distress and growth, three distinct clusters emerged: High Grief (high distress-low growth; n = 16); High Growth (low distress-high growth; n = 32); and Low Impact (low distress-low growth; n = 21). Discriminant function analyses showed that the High Grief cluster differed robustly from the other two groups on several measures of grief adaptation and coping; the differences between the High Growth and Low Impact clusters were less pronounced. High Grief participants sought grief counseling significantly more often whereas the Low Impact grievers preferred medicinal help for symptoms if they sought any professional assistance at all. When High Growth participants sought counseling, they seemed to focus on growth-oriented dimensions rather than mere symptom relief. Of the 11 participants who sought grief counseling for their loss, 10 (91%) found the experience to be helpful. Findings are discussed in the context of meta-analytic studies of the effectiveness of grief counseling.