Nuclear run-on assays carried out in the presence and absence of the RNA polymerase II inhibitor, ~t-amanitin, were used to determine the exact timing of the switch from inhibitor-sensitive transcription catalysed by host RNA polymerase II, to inhibitor-resistant transcription catalysed by the baculovirus-induced RNA polymerase. These studies revealed that the onset of ~-amanitin-resistant transcription is just after 6 h post-infection, simultaneous with the beginning of the late phase of infection. They also showed that transcripts from the p26 gene in the HindIII Q/P region and the p35 gene in the HindlII K/Q region of the viral genome are synthesized by the host RNA polymerase II both early and late in infection. On the other hand, transcripts of the p 10 gene in the HindII! Q/P region and the y transcripts in the HindIII K region are synthesized by the ~-amanitin-resistant, virus-induced RNA polymerase late in infection.

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Background and Objectives As a part of efforts to evaluate eeffectiveness of aortacell lineages derived from the transgenic mice in which expression of the temperature-sensitive SV40 large T antigen has been targeted to vascular smooth muscle, localization of the T antigen gene in chromosome of the established cell lineages was characterized. Expression pattern of p53 in an aorta cell line or those of -actin and the T antigen in the various tissues of the transgenic mice, respectively, were also examined. Materials and Methods Chromosomal DNA obtained from the aorta cell lines, which were derived from the transgenic mice, was analyzed by genomic Southern blot method to identify the transgene in genome. mRNA was prepared from the various tissues of the transgenic mouse and was examined by Northern blot analysis to detect expression of -actin gene. Reverse transcription polymerase chain reaction RT-PCR was also performed to examine transcription pattern of p53 gene in an aorta cell line. Immunohistology for detecting the T antigen expression in the tissues of the transgenic mouse was also carried out. Results Correct integration of the SV40 T antigen transgene in chromosome was observed in two aorta cell lines, although their copy numbers inserted were different from each other. Alternative splicing of the primary p53 RNA was identified in the aorta cells when cultured at the restrictive temperature, but not in the cells at permissive temperature. Several tissues of the transgenic mouse showed expression of the viral oncoprotein T antigen. Conclusion An established aorta cell line may be useful model to study the mechanism regulating the proliferation of vascular smooth cells in mice. Mutant form s of the p53 tumor suppressor protein generated by the translation of the alternatively spliced mRNA might be involved in the blockade of apoptosis in some aorta cells when cultured at the restrictive temperature. However, expression of the viral gene in the tissues of the transgenic mice seemed not to be precisely regulated by temperature-dependent manner. Korean Circulation J 1999 ; 29 5 : 507-516