Constitutive expression of the gene for the cell-specific p48 DNA-binding subunit of pancreas transcription factor 1 in cultured cells is under control of binding sites for transcription factors Sp1 and alphaCbf.

We have cloned and characterized the rat gene that encodes the p48 DNA-binding subunit of pancreas transcription factor 1 (Ptf1), a cell-specific basic region helix-loop-helix (bHLH) protein. The ptf1-p48 gene measures 1.8 kilobases in size and occurs as a single copy in the haploid genome. Run-on transcription assays suggest that this gene is subject to transcriptional control since no activity of its promoter is detected in nonproducing cells. The gene specifies two mRNAs that encode the same protein and originate from transcription initiation at alternative sites. Expression analysis of hybrid genes bearing deletions of the gene's 5'-flanking region fused to a reporter gene defines a promoter region within the gene-proximal 260 base pairs of DNA. The cis-acting elements that control promoter activity include binding sites for transcription factors Sp1 and alphaCbf, a 60-kDa CCAAT box-binding protein. The gene promoter, however, functions not only in exocrine pancreatic cells but also in cells of other origin. No cell-specific transcriptional control element was detected in as much as 10 kilobases of 5'-flanking region. We discuss models of how the cell-specific expression of the endogenous ptf1-p48 gene might be established during development of the animal

Static light scattering and electric birefringence experiments on saltfree solutions of poly(styrenesulfonate)

Static light scattering and electric birefringence measurements on aqueous solutions of charged poly(styrenesulfonate) (PSS) with different molecular weights between 10$^5$ and $1.1 \times 10^6$ g/mol are presented. All experiments were performed in the dilute and the semidilute concentration regime (0.0005 mg/ml $<$ $c$ $<$ 10 mg/ml) at minimum ionic strength (down to $\approx$ 10$^{-6}$ M). The static light scattering experiments show a single broad peak in the scattered intensity. The scattering vectors of these peaks increase with increasing concentrations $c$ and scale either with $c^{1/3}$ or with $c^{1/2}$ only depending on a relative concentration but not on the molecular weight : below about 20 $c^*$ (1 $c^*$ := overlap concentration of extended chains = 1 particle/(contour length $\ell_{\rm c}$)$^3$) we found a $c^{1/3}$ dependence of the scattering vector, above 20 $c^*$ a $c^{1/2}$ law is valid. A similar behaviour has been observed for rigid rods [1]. Our results are compared with previous light-[2, 3], small angle neutron-[4, 5], and small angle X-ray [6] scattering investigations. Nearly all of these studies are in a very good agreement with the $c^{1/3}$-and $c^{1/2}$-law. The relaxation of the electric birefringence signal after an applied rectangular electric field is monoexponential in nearly all cases. Again the concentration 20 $c^*$, independent of the molecular weight, seems to be a critical concentration : below 20 $c^*$ we found a normal (negative) birefringence signal, above an anomal (positive) signal. These results are compared with results of electric birefringence measurements on aqueous solutions of rigid rods [7, 8] and PSS- at different ionic strengths [9-11]. It is claimed that our results can be explained by a small flexibility of strongly elongated PSS–rods which increases slightly with increasing molecular weight and distinctly with raising concentration. The concentration $c^*$ is shown to be a reasonable quantity to describe polyelectrolyte solutions without added salt, independent of the molecular weight, respectively the contour length. By rescaling comparable data published by other authors we can establish the critical concentration 20 $c^*$, which seems to be universally valid

Electro-optic effects of aqueous fd-virus suspensions at very low ionic strength

The orientation in external electric fields of rod-like fd-virus particles (length $\ell = 895$ nm, diameter $d = 9$ nm) in aqueous suspensions is examined by the electric birefringence method. In aqueous suspensions the negatively charged fd-particles are surrounded by a diffuse Debye cloud of counterions, which is characterized by the Debye-Hückel parameter $\kappa$. A special experimental set-up is used to vary the ionic strength of the suspension, i.e. the Debye-Hückel parameter, and therefore the electrostatic interparticle interaction. The birefringence signal $\Delta n$ is measured as a function of the strength and frequency of the applied electric field in suspensions of very low ionic strength (10$^{-6}\,$M-10$^{-4}\,$M). At low field strengths Kerr-behaviour is found. From the dependence of the electric anisotropy $\Delta \alpha_{\rm el}$ on the Debye-Hückel parameter $\kappa$ it is concluded that the orientation of the fd-particles is correlated to an induced dipole due to a deformation of the diffuse Debye cloud. Saturation electric birefringence values are far from that theoretically expected. This can be interpreted as a destruction of the diffuse Debye cloud at high electric fields. At low field strengths the frequency dispersion below 1 kHz of $\Delta n$ of the electrostatically interacting fd-virus suspensions shows anomalous behaviour. This negative electro-optic effect is an evidence for the orientation of the particle's long symmetry axis perpendicular to the applied electric field. The dispersion has a positive maximum at about 2 kHz. This maximum could be explained by different frequency dependencies of the electric polarizabilities parallel and perpendicular to the long symmetry axis of the fd-rods

The p48 DNA-binding subunit of transcription factor PTF1 is a new exocrine pancreas-specific basic helix-loop-helix protein.

We report the isolation of cDNA for the p48 DNA-binding subunit of the heterooligomeric transcription factor PTF1. A sequence analysis of the cDNA demonstrates that p48 is a new member of the family of basic helix-loop-helix (bHLH) transcription factors. The p48 bHLH domain shows striking amino acid sequence similarity with the bHLH domain of proteins that act as developmental regulators, including the twist gene product, myogenic factors and proteins involved in hematopoietic differentiation. We show that reduced p48 synthesis correlates with a diminished expression of genes encoding exocrine pancreas-specific functions. The synthesis of p48 mRNAs, and therefore also the protein, is restricted to cells of the exocrine pancreas in the adult and to the pancreatic primordium in the embryo. Thus the pancreas-specific DNA-binding activity of PTF1 originates from the synthesis of at least one cell-specific component rather than from a cell-specific assembly of more widely distributed proteins

Concordance among digital gene expression, microarrays, and qPCR when measuring differential expression of microRNAs.

Profiling microRNA (miRNA) expression is of widespread interest given the critical role of miRNAs in many cellular functions. Profiling can be achieved via hybridization-based (microarrays), sequencing-based, or amplification-based (quantitative reverse transcription-PCR, qPCR) technologies. Among these, microarrays face the significant challenge of accurately distinguishing between mature and immature miRNA forms, and different vendors have developed different methods to meet this challenge. Here we measure differential miRNA expression using the Affymetrix, Agilent, and Illumina microarray platforms, as well as qPCR (Applied Biosystems) and ultra high-throughput sequencing (Illumina). We show that the differential expression measurements are more divergent when the three types of microarrays are compared than when the Agilent microarray, qPCR, and sequencing technology measurements are compared, which exhibit a good overall concordance