Nucleolar Localization of GLTSCR2/PICT-1 Is Mediated by Multiple Unique Nucleolar Localization Sequences

The human glioma tumor suppressor candidate region 2 gene product, GLTSCR2, also called ‘protein interacting with carboxyl terminus 1’ (PICT-1), has been implicated in the regulation of two major tumor suppressor proteins, PTEN and p53, and reported to bind the membrane-cytoskeleton regulator of cell signaling, Merlin. PICT-1 is a nucleolar protein, conserved among eukaryotes, and its yeast homolog has been functionally associated with ribosomal RNA processing. By means of confocal microscopy of EGFP and myc-tagged PICT-1 fusion proteins, we delineate that the nucleolar localization of PICT-1 is mediated by two independent nucleolar localization sequences (NoLS). Unlike most NoLSs, these NoLSs are relatively long with flexible boundaries and contain arginine and leucine clusters. In addition, we show that PICT-1 exhibits a nucleolar distribution similar to proteins involved in ribosomal RNA processing, yet does not colocalize precisely with either UBF1 or Fibrillarin under normal or stressed conditions. Identification of the precise location of PICT-1 and the signals that mediate its nucleolar localization is an important step towards advancing our understanding of the demonstrated influence of this protein on cell fate and tumorigenesis

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Schizophrenia-associated somatic copy-number variants from 12,834 cases reveal recurrent NRXN1 and ABCB11 disruptions

While germline copy-number variants (CNVs) contribute to schizophrenia (SCZ) risk, the contribution of somatic CNVs (sCNVs)—present in some but not all cells—remains unknown. We identified sCNVs using blood-derived genotype arrays from 12,834 SCZ cases and 11,648 controls, filtering sCNVs at loci recurrently mutated in clonal blood disorders. Likely early-developmental sCNVs were more common in cases (0.91%) than controls (0.51%, p = 2.68e−4), with recurrent somatic deletions of exons 1–5 of the NRXN1 gene in five SCZ cases. Hi-C maps revealed ectopic, allele-specific loops forming between a potential cryptic promoter and non-coding cis-regulatory elements upon 5′ deletions in NRXN1. We also observed recurrent intragenic deletions of ABCB11, encoding a transporter implicated in anti-psychotic response, in five treatment-resistant SCZ cases and showed that ABCB11 is specifically enriched in neurons forming mesocortical and mesolimbic dopaminergic projections. Our results indicate potential roles of sCNVs in SCZ risk

Amino acids 387–478 contain a functional NoLS.

<p>(A) The sequences of myc-tagged PICT-1 deletion mutants are shown. Cellular localization as determined by confocal microscopy is indicated on the right. (B) Confocal microscopic analysis of fusion proteins. 24 hrs after transfection, cells were stained with anti-myc antibody and rhodamine-conjugated secondary antibody. Hoechst stained DNA appears blue. Corresponding differential interference contrast (DIC) images are also shown.</p

PICT-1 substitution mutants within the NoLS spanning amino-acids 347–395 retain the ability to be targeted to the nucleolus.

<p>(A) The sequences of myc-tagged full-length PICT-1 substitution mutants (M1–M6) are shown. Mutated residues are indicated by dotted lines. Cellular localization as determined by confocal microscopy is indicated on the right. (B) Confocal microscopic analysis of fusion proteins. 24 hrs after transfection, cells were stained with anti-myc antibody and rhodamine-conjugated secondary antibody. Hoechst stained DNA appears blue. Corresponding differential interference contrast (DIC) images are also shown.</p

Schematic representation of PICT-1 with its predicted monopartite (m) and bipartite (b) NLSs.

<p>Previously reported truncation mutants are shown with their cellular localization indicated on the right, ^a refers to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030825#pone.0030825-Kalt1" target="_blank">[19]</a> and ^b refers to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030825#pone.0030825-Yim1" target="_blank">[6]</a>. Shadowing denotes the putative nucleolar targeting sequence (aa 347–386) inferred from the localization of these mutants.</p