Small nucleolar RNAs (snoRNAs) associate with specific proteins forming small nucleolar ribonucleoprotein (snoRNP) particles, which are essential for ribosome biogenesis. The snoRNAs are transcribed, processed, and assembled in snoRNPs in the nucleoplasm. Mature particles are then transported to the nucleolus. In yeast, 3'-end maturation of snoRNAs involves the activity of Rnt1p endonuclease an...

The protein kinase TOR (target of rapamycin) controls several steps of ribosome biogenesis, including gene expression of rRNA and ribosomal proteins, and processing of the 35S rRNA precursor, in the budding yeast Saccharomyces cerevisiae. Here we show that TOR also regulates late stages of ribosome maturation in the nucleoplasm via the nuclear GTP-binding protein Nog1. Nog1 formed a complex tha...

The control of human ribosomal protein L22 (rpL22) to enter into the nucleolus and its ability to be assembled into the ribosome is regulated by its sequence. The nuclear import of rpL22 depends on a classical nuclear localization signal of four lysines at positions 13-16. RpL22 normally enters the nucleolus via a compulsory sequence of KKYLKK (I-domain, positions 88-93). An acidic residue clus...

Transcription of rRNA genes (rDNAs) in the nucleolus is regulated by epigenetic chromatin modifications including histone H3 lysine (de)methylation. Here we show that LegAS4, a Legionella pneumophila type IV secretion system (TFSS) effector, is targeted to specific rDNA chromatin regions in the host nucleolus. LegAS4 promotes rDNA transcription, through its SET-domain (named after Drosophila Su...

In response to a shortage of intracellular energy, mammalian cells reduce energy consumption and induce cell cycle arrest, both of which contribute to cell survival. Here we report that a novel nucleolar pathway involving the energy-dependent nucleolar silencing complex (eNoSC) and Myb-binding protein 1a (MYBBP1A) is implicated in these processes. Namely, in response to glucose starvation, eNoS...

The nucleolus is the most obvious and clearly differentiated nuclear sub-compartment. It is where ribosome biogenesis takes place, but it is becoming clear that the nucleolus also has non-ribosomal functions. In this review we discuss recent progress in our understanding of how both ribosome biosynthesis and some non-ribosomal functions relate to observable nucleolar structure. We still do not ...

Nopp140 is a nucleolar phosphoprotein of 140 kd that we originally identified and purified as a nuclear localization signal (NLS)-binding protein. Molecular characterization revealed a 10-fold repeated motif of highly conserved acidic serine clusters that contain an abundance of phosphorylation consensus sites for casein kinase II (CK II). Indeed, Nopp140 is one of the most phosphorylated prote...

The analysis of microsporogenesis in endogamous plants of popcorn (S5 to S7) showed several and distinct interchanges which involve the nucleolus organizer (chromosome 6). The detection of cells with interchanges was facilitated by the presence of two nucleoli of different sizes in contrast to normal ones with a single big nucleolus. Interchange points do not always seem to be at the same place...

We consider classes of cooperative games. We show that we can eeciently compute an allocation in the intersection of the prekernel and the least core of the game if we can eeciently compute the minimum excess for any given allocation. In the case where the prekernel of the game contains exactly one core vector, our algorithm computes the nucleolus of the game. This generalizes both a recent res...

We study the “airport problem”, which is concerned with sharing the cost of an airstrip among agents who need airstrips of different lengths. We address whether different formulations of consistency and converse consistency axioms provide strategic justifications for different rules. We propose Right-endpoint Subtraction (RS) bilateral consistency and RS converse consistency in the airport prob...