Isolation and analysis of a human cDNA highly homologous to the yeast gene encoding L17A ribosomal protein

Identification of cellular factors binding to acetylated HIV-1 integrase

The viral protein integrase (IN) catalyzes the integration of the HIV-1 cDNA into the host cellular genome. We have recently demonstrated that IN is acetylated by a cellular histone acetyltransferase, p300, which modifies three lysines located in the C-terminus of the viral factor (Cereseto et al. in EMBO J 24:3070-3081, 2005). This modification enhances IN catalytic activity, as demonstrated by in vitro assays. Consistently, mutations introduced in the targeted lysines greatly decrease the efficiency of HIV-1 integration. Acetylation was proven to regulate protein functions by modulating protein-protein interactions. HIV-1 to efficiently complete its replication steps, including the integration reaction, requires interacting with numerous cellular factors. Therefore, we sought to investigate whether acetylation might modulate the interaction between IN and the cellular factors. To this aim we performed a yeast two-hybrid screening that differs from the screenings so far performed (Rain et al. in Methods 47:291-297, 2009; Studamire and Goff in Retrovirology 5:48, 2008) for using as bait IN constitutively acetylated. From this analysis we have identified thirteen cellular factors involved in transcription, chromatin remodeling, nuclear transport, RNA binding, protein synthesis regulation and microtubule organization. To validate these interactions, binding assays were performed showing that acetylation increases the affinity of IN with specific factors. Nevertheless, few two-hybrid hits bind with the same affinity the acetylated and the unmodified IN. These results further underlie the relevance of IN post-translational modification by acetylation in HIV-1 replication cycle.

Splice-site pairing is an intrinsically high fidelity process

The extensive alternative splicing in higher eukaryotes has initiated a debate whether alternative mRNA isoforms are generated by an inaccurate spliceosome or are the consequence of highly degenerate splice sites within the human genome. Here, we established a quantitative assay to evaluate the accuracy of splice-site pairing by determining the number of incorrect exon-skipping events made from constitutively spliced pre-mRNA transcripts. We demonstrate that the spliceosome pairs exons with an astonishingly high degree of accuracy that may be limited by the quality of pre-mRNAs generated by RNA pol II. The error rate of exon pairing is increased by the effects of the neurodegenerative disorder spinal muscular atrophy because of reduced levels of Survival of Motor Neuron, a master assembler of spliceosomal components. We conclude that all multi-intron-containing genes are alternatively spliced and that the reduction of SMN results in a general splicing defect that is mediated through alterations in the fidelity of splice-site pairing.

Developmental changes in the fetal pig transcriptome

Growth and development of pig fetuses is dependent on the coordinated expression of multiple genes. Between 21 and 45 days of gestation, fetuses experience increasing growth rates that can result in uterine crowding and increased mortality. We used differential display reverse transcription-PCR (DDRT-PCR) to identify differentially expressed genes in pig fetuses at 21, 35, and 45 days of gestation. Pig cDNAs were identified with homologies to CD3 gamma-subunit, collagen type XIV alpha1, complement component C6, craniofacial developmental protein 1, crystallin-gammaE, DNA binding protein B, epsilon-globin, formin binding protein 2, ribosomal protein L23, small acidic protein, secreted frizzled related protein 2, titin, vitamin D binding protein, and two hypothetical protein products. Two novel expressed sequence tags (ESTs) were also identified. Expression patterns were confirmed for eight genes, and spatiotemporal expression of three genes was evaluated. We identified novel transcriptome changes in fetal pigs during a period of rapid growth. These changes involved genes with a spectrum of proposed functions, including musculoskeletal growth, immune system function, and cellular regulation. This information can ultimately be used to enhance production efficiency through improved pig growth and survival.

Genomic organization and chromosome location of the murine Rpl23 gene

The mouse gene coding for ribosomal protein L23 (Rpl23) has been fully sequenced, including 580 bp of the 5' upstream region. The 5-kb gene comprises 5 exons and contains an unusually long (3,153 bp) third intron. The gene was mapped to the distal region of mouse chromosome 11, homologous to human chromosome 17q21-->q22.

The Drosophila melanogaster ribosomal protein L17A-encoding gene

The structure and sequence of the gene encoding the Drosophila melanogaster homolog of the human and yeast large-subunit ribosomal protein L17A (rpL17A) is presented. The deduced amino acid (aa) sequence of 140 residues exhibits 87% and 77% identity to that of the human (140 aa) and yeast (137 aa) rpL17As, respectively. The D. melanogaster rpL17A gene is single copy and maps at 58F6-59A3, a chromosome region encompassing a previously characterized Minute locus, M(2)I. Despite this extensive homology in their protein products, the D. melanogaster and yeast rpL17A genes display different exon-intron structures, with the first D. melanogaster intron mapping within the 5'-untranslated mRNA leader. The rpL17A gene gives rise to a single 600-nucleotide transcript present throughout development, and is located close to another similarly expressed gene. The 5' end of the D. melanogaster rpL17A mRNA contains a polypyrimidine tract displayed by several mammalian rp genes and involved in translational control of their expression.