Formas de establecimiento en el mercado extranjero: factores determinantes para el caso de la multinacional india Tata

En este trabajo trataremos de explicar los motivos que hay detrás de la forma de inversión directa en el exterior (IDE) a través de adquisiciones frente a la opción de establecerse en el mercado extranjero con recursos propios. Para una muestra de 117 decisiones de IDE efectuadas por la multinacional india Tata en 43 países, los resultados obtenidos indican que la intensidad tecnológica del sector, el riesgo asociado al país de destino, el atractivo del mercado extranjero, la experiencia previa internacional o las exportaciones indias al país donde se decide invertir son factores que condicionan dicha elección.

真核生物TATA框的折叠结构特征

通过对真核生物142个基因的部分启动子序列的折叠模型进行分析研究,结果表明,这些基因的TATA框在折叠结构模型中所表现的茎环结构特征有利于与反式作用因子和RNA聚合酶的识别及其相互作用。

Frequency distribution of TATA box and extension sequences on human promoters

TATA box is one of the most important transcription factor binding sites. But the exact sequences of TATA box are still not very clear yet. In this study, we conducted a dedicated analysis on the frequency distribution of TATA Box and its extension sequences on human promoters. Sixteen TATA elements derived from TATA Box motif, TATAWAWN, were classified into three distribution patterns: peak, bottom-peak and bottom. Fourteen TATA extension sequences (up to two base extensions) were predicted to be the new TATA Box elements because of their high motif factors, which indicate their statistical significance. Statistical analysis on the promoters of mouse, zebrafish and drosophila melanogaster verified seven of these elements. It was also observed that the distribution of TATA elements on the promoters of housekeeping genes are very similar with their distribution on the promoters of tissue specific genes in human.

Regulation of XMyoDa transcription by the binding of XMEF2A to the TATA box

MEF2 is a $\underline{\rm m}$yocyte-specific $\underline{\rm e}$nhancer-binding $\underline{\rm f}$actor that binds a conserved DNA sequence, CTA(A/T)$\sb4$TAG. A MEF2 binding site in the XMyoDa promoter overlaps with the TATA box and is required for muscle specific expression. To examine the potential role of MEF2 in the regulation of MyoD transcription during early development, the appearance of MEF2 binding activity in developing Xenopus embryos was analyzed with the electrophoretic mobility shift assay. Two genes were isolated from a X. Laevis stage 24 cDNA library that encode factors that bind the XMyoDa TFIID/MEF2 site. Both genes are highly homologous to each other, belong to the MADS ($\underline{\rm M}$CM1-$\underline{\rm A}$rg80-agamous-$\underline{\rm d}$eficiens-$\underline{\rm S}$RF) protein family, and most highly related to the mammalian MEF2A gene, hence they are designated as XMEF2A1 and XMEF2A2. Proteins encoded by both cDNAs form specific complexes with the MEF2 binding site and show the same binding specificity as the endogenous MEF2 binding activity. XMEF2A transcripts accumulate preferentially in developing somites after the appearance of XMyoD transcripts. XMEF2 protein begins to accumulate in somites at tailbud stages. Transcriptional activation of XMyoD promoter by XMEF2A required only the MADS box and MEF2-specific domain when XMEF2A is bound at the TATA box. However, a different downstream transactivation domain was required when XMEF2A activates transcription through binding to multiple upstream sites. These results suggest that different activation mechanisms are involved, depending on where the factor is bound. Mutations in several basic amino acid clusters in the MADS box inhibit DNA binding suggesting these amino acids are essential for DNA binding. Mutation of Thr-20 and Ser-36 to the negatively charged amino acid residue, aspartic acid, abolish DNA binding. XMEF2A activity may be regulated by phosphorylation of these amino acids. A dominant negative mutant was made by mutating one of the basic amino acid clusters and deleting the downstream transactivation domain. In vivo roles of MEF2 in the regulation of MyoD transcription were investigated by overexpression of wild type MEF2 and dominant negative mutant of XMEF2A in animal caps and assaying for the effects on the level of expression of MyoD genes. Overexpression of MEF2 activates the transcription of endogenous MyoD gene family while expression of a dominant negative mutant reduces the level of transcription of XMRF4 and myogenin genes. These results suggest that MEF2 is downstream of MyoD and Myf5 and that MEF2 is involved in maintaining and amplifying expression of MyoD and Myf5. MEF2 is upstream of MRF4 and myogenin and plays a role in activating their expression. ^

Architectural specificity in chromatin structure at the TATA box in vivo: Nucleosome displacement upon β-phaseolin gene activation

Extensive studies of the β-phaseolin (phas) gene in transgenic tobacco have shown that it is highly active during seed embryogenesis but is completely silent in leaf and other vegetative tissues. In vivo footprinting revealed that the lack of even basal transcriptional activity in vegetative tissues is associated with the presence of a nucleosome that is rotationally positioned with base pair precision over three phased TATA boxes present in the phas promoter. Positioning is sequence-dependent because an identical rotational setting is obtained upon nucleosome reconstitution in vitro. A comparison of DNase I and dimethyl sulfate footprints in vivo and in vitro strongly suggests that this repressive chromatin architecture is remodeled concomitant with gene activation in the developing seed. This leads to the disruption of histone-mediated DNA wrapping and the assembly of the TATA boxes into a transcriptionally competent nucleoprotein complex.

An interplay between TATA box-binding protein and transcription factors IIE and IIA modulates DNA binding and transcription

The basal transcription factor IIE (TFIIE) is thought to be one of the last factors to be assembled into a preinitiation complex (PIC) at eukaryotic promoters after RNA polymerase II and TFIIF have been incorporated. It was shown that a primary function of TFIIE is to recruit and cooperate with TFIIH in promoter melting. Here, we show that the large subunit of TFIIE (E56) can directly stimulate TBP binding to the promoter in the absence of other basal factors. The zinc-finger domain of E56, required for transcriptional activity, is critical for this function. In addition, the small subunit of TFIIE (E34) directly contacts DNA and TFIIA and thus providing a second mechanism for TFIIE to help binding of a TBP/IIA complex to the promoter, the first critical step in the PIC assembly. These studies suggest an alternative PIC assembly pathway in which TFIIE affects both TBP and TFIIH functions during initiation of RNA synthesis.

The importin/karyopherin Kap114 mediates the nuclear import of TATA-binding protein

Two high copy suppressors of temperature-sensitive TATA-binding protein (TBP) mutants were isolated. One suppressor was TIF51A, which encodes eukaryotic translation initiation factor 5A. The other high copy suppressor, YGL241W, also known as KAP114, is one of 14 importin/karyopherin proteins in yeast. These proteins mediate the transport of specific macromolecules into and out of the nucleus. Cells lacking Kap114 partially mislocalize TBP to the cytoplasm. Kap114 binds TBP in vitro, and binding is disrupted in the presence of GTPγS. Therefore, Kap114 is an importer of TBP into the nucleus, but alternative import pathways must also exist.

Cloning of the cDNA for the TATA-binding protein-associated factorII170 subunit of transcription factor B-TFIID reveals homology to global transcription regulators in yeast and Drosophila

The human transcription factor B-TFIID is comprised of TATA-binding protein (TBP) in complex with one TBP-associated factor (TAF) of 170 kDa. We report the isolation of the cDNA for TAFII170. By cofractionation and coprecipitation experiments, we show that the protein encoded by the cDNA encodes the TAF subunit of B-TFIID. Recombinant TAFII170 has (d)ATPase activity. Inspection of its primary structure reveals a striking homology with genes of other organisms, yeast MOT1, and Drosophila moira, which belongs to the Trithorax group. Both homologs were isolated in genetic screens as global regulators of pol II transcription. This supports our classification of B-TFIID as a pol II transcription factor and suggests that specific TBP–TAF complexes perform distinct functions during development.

RAP74 induces promoter contacts by RNA polymerase II upstream and downstream of a DNA bend centered on the TATA box

RAP74, the large subunit of transcription factor IIF, associates with a preinitiation complex containing RNA polymerase II (pol II) and other general initiation factors. We have mapped the location of RAP74 in close proximity to promoter DNA at similar distances both upstream and downstream of a DNA bend centered on the TATA box. Binding of RAP74 induces a conformational change that affects the position of pol II relative to that of the DNA. This reorganization of the preinitiation complex minimally requires the N-terminal region of RAP74 containing both its RAP30-binding domain and another region necessary for accurate transcription in vitro. We propose a role for RAP74 in controlling the topological organization of the pol II preinitiation complex.