The high-mobility group protein 14 (HMG-14) is a non-histone chromosomal protein that is preferentially associated with transcriptionally active chromatin. To assess the effect of HMG-14 on transcription by RNA polymerase II, in vivo-assembled chromatin with elevated amounts of HMG-14 was obtained. Here it is shown that HMG-14 enhanced transcription on chromatin templates but not on DNA templates. This protein stimulated the rate of elongation by RNA polymerase II but not the level of initiation of transcription. These findings suggest that the association of HMG-14 with nucleosomes is part of the cellular process involved in the generation of transcriptionally active chromatin.

Of 38 adult patients admitted for first-episode psychosis, 20 reported childhood abuse, with equal prevalence in men and women. Patients with histories of childhood abuse had significantly more dissociative symptoms, but not more severe psychiatric symptoms. Childhood abuse was not related to rate of recovery and was only marginally related to longer stays in hospital. Although childhood abuse did not affect recovery during first-episode psychosis, it may contribute to a chronic course in some patients.

The integrase (IN) protein of the human immunodeficiency virus mediates integration of the viral DNA into the cellular genome. In vitro, this reaction can be mimicked by using purified recombinant IN and model DNA substrates. IN mediates two reactions: an endonucleolytic cleavage at each 3 end of the proviral DNA (terminal cleavage) and the joining of the linear viral DNA to 5 phosphates in the target DNA (strand transfer). Previous investigators have shown that purified IN requires Mn 2؉ or Mg 2؉ to promote strand transfer in vitro, although Mg 2؉ is the likely metal cofactor in vivo. IN activity in the presence of Mg 2؉ in vitro requires high IN concentrations and low concentrations of salt. Here, we show that the viral nucleocapsid protein NCp7 allows efficient IN-mediated strand transfer in the presence of Mg 2؉ at low enzyme concentrations. This potentiating effect appears to be unique to NCp7, as other small DNA-binding proteins, while capable of stimulating integration in the presence of Mn 2؉ , all failed to stimulate strand transfer in the presence of Mg 2؉ .

We have studied the initiation of transcription in vitro by RNA polymerase II on simian virus 40 (SV40) minichromosomal templates isolated from infected cells. The efficiency and pattern of transcription from the chromatin templates were compared with those from viral DNA templates by using two in vitro transcription systems, either HeLa whole-cell extract or basal transcription factors, RNA polymerase II, and one of two SV40 promoter-binding transcription factors, LSF and Spl. Dramatic increases in numbers of transcripts upon addition of transcription extract and different patterns of usage of the multiple SV40 initiation sites upon addition of Spl versus LSF strongly suggested that transcripts were being initiated from the minichromosomal templates in vitro. That the majority of transcripts from the minichromosomes were due to initiation de novo was demonstrated by the efficient transcription observed in the presence of a-amanitin, which inhibited minichromosome-associated RNA polymerase II, and an a-amanitin-resistant RNA polymerase II, which initiated transcription in vitro. The pattern of transcription from the SV40 late and early promoters on the minichromosomal templates was similar to the in vivo pattern of transcription during the late stages of viral infection and was distinct from the pattern of transcription generated from viral DNA in vitro. In particular, the late promoter of the minichromosomal templates was transcribed with high efficiency, similar to viral DNA templates, while the early-early promoter of the minichromosomal templates was inhibited 10-to 15-fold. Finally, the number of minichromosomes competent to initiate transcription in vitro exceeded the amount actively being transcribed in vivo.Within eukaryotic cells, gene expression is regulated in the context of chromatin, a complex of genomic DNA, histones, and nonhistone proteins. Localized biochemical and structural changes of the chromatin have been correlated with the ability of individual genes to be actively transcribed. Such changes include higher concentrations of high-mobility-group proteins, modified histones, methylated cytosine residues (for reviews, see references 53 and 73), and the appearance of DNase I-hypersensitive sites, both 3' and 5' to the gene (for reviews, see references 20 and 29). Hypersensitivity to DNase I is believed to be due to the binding of specific transcription factors to promoter elements and to the displacement or the specific positioning of nucleosomes. Therefore, it is argued that chromatin plays a role in the regulation of gene expression.To investigate directly the role of chromatin in regulating transcription, in vitro assays have been developed to study the initiation and elongation of transcription on chromatin templates. Such in vitro transcription studies require substantial quantities of a defined DNA complexed into nucleosomes. Several previous studies have used as templates chromatin assembled in vitro by incubating DNA with either * Corresponding author.t Present address: