Delayed response of hermit crabs carrying anemones to a benthic impact experiment at the deep-sea nodule fields of the Peru Basin?

The deep Peru Basin is characterised by a unique abyssal scavenging community featuring large numbers of hermit crabs (Probeebei mirabilis, Decapoda, Crustacea). These are atypical hermit crabs, not carrying a shell, but on some occasions carrying an anemone (Actiniaria). The reason why some hermit crabs carry or not carry anemones is thought to be indicative of a changed environment, outweighing the cost/benefit of their relationship. Here we present the temporal variation of abundances of P. mirabilis with and without anemones, spanning more than two decades, following a benthic impact experiment. An overall decrease in hermit crab densities was observed, most noticeable and significant after 26 years and characterised by a loss of Actiniaria on the Probeebei mirabilis' pleon. Whether this is a delayed response to the benthic impact experiment carried out 26 years' prior or a natural variation in the population remains to be corroborated by an extension of the time-series. Attention is drawn to the limitations of our knowledge over time and space of the abyssal community dynamics and the urgent necessity to fill in these gaps prior to any type of deep-sea exploitation.

Identification of transcription factories in nuclei of HeLa cells transiently expressing the Us11 gene of herpes simplex virus type 1

Nuclear distribution and migration of herpes simplex virus type 1 Us11 transcripts were studied in transient expression at the ultrastructural level and compared to that of RNA polymerase II protein. Transcription was monitored by autoradiography following a short pulse with tritiated uridine. Us11 transcripts accumulated mainly over the foci of intermingled RNP fibrils as demonstrated by the presence of silver grains localizing incorporated radioactive uridine superimposed to these structures in which the presence of Us11 RNA and poly(A) tails was previously demonstrated. Silver grains were also scattered over the remaining nucleoplasm but not in the clusters of interchromatin granules, and over the dense fibrillar component of the nucleolus as in control, nontransfected HeLa cells. Pulse-chase experiments revealed the transient presence of migrating RNA in the clusters of interchromatin granules. RNA polymerase II was revealed by immunogold labeling following the use of two monoclonal antibodies: mAb H5, which recognizes the hyperphosphorylated form of the carboxy-terminal domain (CTD) of the molecule, and mAb 7C2, which recognizes both its hyperphosphorylated and unphosphorylated forms. The two mAbs bind to the newly formed Us11 transcription factories and the clusters of interchromatin granules of transfected cells. In control cells, however, clusters of interchromatin granules were labeled with mAb H5 but not with mAB 7C2. Taken together, our data demonstrate the involvement of the clusters of interchromatin granules in the intranuclear migration of Us11 RNA in transient expression. They also suggest the occurrence of changes in the accessibility of the RNA polymerase II CTD upon expression of the Us11 gene after transfection by exposing some epitopes, otherwise masked in nontransfected cells.

Antimalarial remedies in French Guiana: a knowledge attitudes and practices study

A "knowledge attitudes and practices" study about malaria treatments was undertaken in French Guiana, along with an ethnopharmacological study. One hundred and seventeen people from five different groups and nationalities (Creole, Palikur, Galibi, Brazilian, and European) answered the questionnaire. The results were analysed using univariate and multivariate statistical analysis. First, we evaluated the overall knowledge about malaria from the interviewed people. According to bio-medical concepts, we noticed that they have a good knowledge of this illness. Secondly, we studied the treatment used by sick people during their last malaria attack. We demonstrated that, although bio-medical treatment is available in this area, people use both modern drugs and traditional remedies. Finally, preventive attitudes have been examined. One-third of the interviewed people drink regularly some herbal remedy to prevent febrile illnesses and malaria, thus displaying a strong concern about this disease. The ethnopharmacological study highlighted the frequent use of traditional remedies, along with their mode of preparation and administration. A total of 34 different species (both from flora and fauna) have been registered as antimalarial. Twenty-seven are used for curative purposes, 20 as preventive and 13 of them are used for both purposes. Quassia amara (Simaroubaceae) whose antimalarial activity has already been demonstrated was the species most frequently used as antimalarial for curative and preventive purposes.

Mammalian cell lines expressing functional RNA polymerase II tagged with the green fluorescent protein

RNA polymerase II is a multi-subunit enzyme responsible for transcription of most eukaryotic genes. It associates with other complexes to form enormous multifunctional ‘holoenzymes’ involved in splicing and polyadenylation. We wished to study these different complexes in living cells, so we generated cell lines expressing the largest, catalytic, subunit of the polymerase tagged with the green fluorescent protein. The tagged enzyme complements a deficiency in tsTM4 cells that have a temperature-sensitive mutation in the largest subunit. Some of the tagged subunit is incorporated into engaged transcription complexes like the wild-type protein; it both resists extraction with sarkosyl and is hyperphosphorylated at its C terminus. Remarkably, subunits bearing such a tag can be incorporated into the active enzyme, despite the size and complexity of the polymerizing complex. Therefore, these cells should prove useful in the analysis of the dynamics of transcription in living cells.

Isolation and characterization of monoclonal antibodies directed against subunits of human RNA polymerases I, II, and III

Human nuclei contain three different RNA polymerases: polymerases I, II, and III. Each polymerase is a multi-subunit enzyme with 12-17 subunits. The localization of these subunits is limited by the paucity of antibodies suitable for immunofluorescence. We now describe eight different monoclonal antibodies that react specifically with RPB6 (also known as RPA20, RPB14.4, or RPC20), RPB8 (RPA18, RPB17, or RPC18), RPC32, or RPC39 and which are suitable for such studies. Each antibody detects one specific band in immunoblots of nuclear extracts; each also immunoprecipitates large complexes containing many other subunits. When used for immunofluorescence, antibodies against the subunits shared by all three polymerases (i.e., RPB6, RPB8) gave a few bright foci in nucleoli and nucleoplasm, as well as many fainter nucleoplasmic foci; all the bright foci were generally distinct from speckles containing Sm antigen. Antibodies against the two subunits found only in polymerase III (i.e., RPC32, RPC39) gave a few bright and many faint nucleoplasmic foci, but no nucleolar foci. Growth in two transcriptional inhibitors-5, 6-dichloro-1-beta-d-ribofuranosylbenzimidazole and actinomycin D-led to the redistribution of each subunit in a characteristic manner.

Interactions between the full complement of human RNA polymerase II subunits

As an approach to elucidating the rules governing the assembly of human RNA polymerase II (hRPB), interactions between its subunits have been systematically analyzed. Eleven of the 12 expected hRPB subunits have previously been tested for reciprocal interactions (J. Biol. Chem. 272 (1997) 16815-16821). We now report the results obtained for the last subunit (hRPB4; Mol. Cell. Biol. 18 (1998) 1935-1945) and propose an essentially complete picture of the potential interactions occurring within hRPB. Finally, complementation experiments in yeast indicated that hRPB4 expression efficiently cured both heat and cold-sensitivity of RPB4-lacking strains, supporting the existence of conserved functional subunit interactions.

Transcription-independent phosphorylation of the RNA polymerase II C-terminal domain (CTD) involves ERK kinases (MEK1/2)

The largest subunit of the mammalian RNA polymerase II possesses a C-terminal domain (CTD) consisting of 52 repeats of the consensus sequence, Tyr(1)-Ser(2)-Pro(3)-Thr(4)-Ser(5)-Pro(6)-Ser(7). Phosphorylation of the CTD is known to play a key role in gene expression. We now show that treatments such as osmotic and oxidative shocks or serum stimulation generate a new type of phosphorylated subunit, the IIm form. This IIm form might be generated in vivo by ERK-type MAP kinase phosphorylation as: (i) ERK1/2 are major CTD kinases found in cell extracts; (ii) the immunoreactivity of the IIm form against a panel of monoclonal antibodies indicates that the CTD is exclusively phosphorylated on Ser-5 in the repeats, like RNA polymerase II phosphorylated in vitro by an ERK1/2; and (iii) the IIm form does not appear when ERK activation is prevented by treating cells with low concentrations of highly specific inhibitors of MEK1/2. Since the IIm subunit is not affected by inhibition of transcription and is not bound to chromatin, it does not participate in transcription.

EWS, but not EWS-FLI-1, is associated with both TFIID and RNA polymerase II: interactions between two members of the TET family, EWS and hTAFII68, and subunits of TFIID and RNA polymerase II complexes

The t(11;22) chromosomal translocation specifically linked to Ewing sarcoma and primitive neuroectodermal tumor results in a chimeric molecule fusing the amino-terminus-encoding region of the EWS gene to the carboxyl-terminal DNA-binding domain encoded by the FLI-1 gene. As the function of the protein encoded by the EWS gene remains unknown, we investigated the putative role of EWS in RNA polymerase II (Pol II) transcription by comparing its activity with that of its structural homolog, hTAFII68. We demonstrate that a portion of EWS is able to associate with the basal transcription factor TFIID, which is composed of the TATA-binding protein (TBP) and TBP-associated factors (TAFIIs). In vitro binding studies revealed that both EWS and hTAFII68 interact with the same TFIID subunits, suggesting that the presence of EWS and that of hTAFII68 in the same TFIID complex may be mutually exclusive. Moreover, EWS is not exclusively associated with TFIID but, similarly to hTAFII68, is also associated with the Pol II complex. The subunits of Pol II that interact with EWS and hTAFII68 have been identified, confirming the association with the polymerase. In contrast to EWS, the tumorigenic EWS-FLI-1 fusion protein is not associated with either TFIID or Pol II in Ewing cell nuclear extracts. These observations suggest that EWS and EWS-FLI-1 may play different roles in Pol II transcription.

Interactions between the human RNA polymerase II subunits

As an initial approach to characterizing the molecular structure of the human RNA polymerase II (hRPB), we systematically investigated the protein-protein contacts that the subunits of this enzyme may establish with each other. To this end, we applied a glutathione S-transferase-pulldown assay to extracts from Sf9 insect cells, which were coinfected with all possible combinations of recombinant baculoviruses expressing hRPB subunits, either as untagged polypeptides or as glutathione S-transferase fusion proteins. This is the first comprehensive study of interactions between eukaryotic RNA polymerase subunits; among the 116 combinations of hRPB subunits tested, 56 showed significant to strong interactions, whereas 60 were negative. Within the intricate network of interactions, subunits hRPB3 and hRPB5 play a central role in polymerase organization. These subunits, which are able to homodimerize and to interact, may constitute the nucleation center for polymerase assembly, by providing a large interface to most of the other subunits.

Heat-shock inactivation of the TFIIH-associated kinase and change in the phosphorylation sites on the C-terminal domain of RNA polymerase II

The C-terminal domain (CTD) of the RNA polymerase II largest subunit (RPB1) plays a central role in transcription. The CTD is unphosphorylated when the polymerase assembles into a preinitiation complex of transcription and becomes heavily phosphorylated during promoter clearance and entry into elongation of transcription. A kinase associated to the general transcription factor TFIIH, in the preinitiation complex, phosphorylates the CTD. The TFIIH-associated CTD kinase activity was found to decrease in extracts from heat-shocked HeLa cells compared to unstressed cells. This loss of activity correlated with a decreased solubility of the TFIIH factor. The TFIIH-kinase impairment during heat-shock was accompanied by the disappearance of a particular phosphoepitope (CC-3) on the RPB1 subunit. The CC-3 epitope was localized on the C-terminal end of the CTD and generated in vitro when the RPB1 subunit was phosphorylated by the TFIIH-associated kinase but not by another CTD kinase such as MAP kinase. In apparent discrepancy, the overall RPB1 subunit phosphorylation increased during heat-shock. The decreased activity in vivo of the TFIIH kinase might be compensated by a stress-activated CTD kinase such as MAP kinase. These results also suggest that heat-shock gene transcription may have a weak requirement for TFIIH kinase activity.

In vivo degradation of RNA polymerase II largest subunit triggered by alpha-amanitin

Alpha-Amanitin is a well-known specific inhibitor of RNA polymerase II (RNAPII) in vitro and in vivo. It is a cyclic octapeptide which binds with high affinity to the largest subunit of RNAPII, RPB1. We have found that in murine fibroblasts exposure to alpha-amanitin triggered degradation of the RPB1 subunit, while other RNAPII subunits, RPB5 and RPB8, remained almost unaffected. Transcriptional inhibition in alpha-amanitin-treated cells was slow and closely followed the disappearance of RPB1. The degradation rate of RPB1 was alpha-amanitin dose dependent and was not a consequence of transcriptional arrest. Alpha-Amanitin-promoted degradation of RPB1 was prevented in cells exposed to actinomycin D, another transcriptional inhibitor. Epitope-tagged recombinant human RPB1 subunits were expressed in mouse fibroblasts. In cells exposed to alpha-amanitin the wild-type recombinant subunit was degraded like the endogenous protein, but a mutated alpha-amanitin-resistant subunit remained unaffected. Hence, alpha-amanitin did not activate a proteolytic system, but instead its binding to mRPB1 likely represented a signal for degradation. Thus, in contrast to other inhibitors, such as actinomycin D or 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole, which reversibly act on transcription, inhibition by alpha-amanitin cannot be but an irreversible process because of the destruction of RNAPII.

The gene (POLR2L) encoding the hRPB7.6 subunit of human RNA polymerase

The gene (POLR2L) encoding a 7.6-kDa subunit (hRPB7.6) of human RNA polymerase has been cloned. It compromises two exons, 116 and 227 bp, respectively, interspaced with an intron of about 2.1 kb. This gene, whose localization has been assigned to the short arm of chromosome 11 (position 11p15), is transcribed in HeLa cells as one major messenger RNA, which encodes a 67-residue polypeptide (7645 Da) that shares strong homologies with the corresponding subunits of other eukaryotic and archaeal RNA polymerase subunits. Like its yeast counterpart (ABC10 beta, encoded by the RPB10 gene), the hRPB7.6 subunit may be shared by all three classes of human nuclear RNA polymerase. Cysteine residues characteristic of an atypical zinc-binding domain are conserved in the homologous sequences of all six species analyzed. A small, related RNA polymerase subunit from vaccinia virus exhibits an identical set of cysteines, suggesting that these residues may be contribute to a crucial function in the multimeric RNA polymerases.

Four subunits that are shared by the three classes of RNA polymerase are functionally interchangeable between Homo sapiens and Saccharomyces cerevisiae

Four cDNAs encoding human polypeptides hRPB7.0, hRPB7.6, hRPB17, and hRPB14.4 (referred to as Hs10 alpha, Hs10 beta, Hs8, and Hs6, respectively), homologous to the ABC10 alpha, ABC10 beta, ABC14.5, and ABC23 RNA polymerase subunits (referred to as Sc10 alpha, Sc10 beta, Sc8, and Sc6, respectively) of Saccharomyces cerevisiae, were cloned and characterized for their ability to complement defective yeast mutants. Hs10 alpha and the corresponding Sp10 alpha of Schizosaccharomyces pombe can complement an S. cerevisiae mutant (rpc10-delta::HIS3) defective in Sc10 alpha. The peptide sequences are highly conserved in their carboxy-terminal halves, with an invariant motif CX2CX12RCX2CGXR corresponding to a canonical zinc-binding domain. Hs10 beta, Sc10 beta, and the N subunit of archaeal RNA polymerase are homologous. An invariant CX2CGXnCCR motif presumably forms an atypical zinc-binding domain. Hs10 beta, but not the archaeal subunit, complemented an S. cerevisiae mutant (rpb10-delta 1::HIS3) lacking Sc10 beta. Hs8 complemented a yeast mutant (rpb8-delta 1::LYS2) defective in the corresponding Sc8 subunit, although with a strong thermosensitive phenotype. Interspecific complementation also occurred with Hs6 and with the corresponding Dm6 cDNA of Drosophila melanogaster. Hs6 cDNA and the Sp6 cDNA of S. pombe are dosage-dependent suppressors of rpo21-4, a mutation generating a slowly growing yeast defective in the largest subunit of RNA polymerase II. Finally, a doubly chimeric S. cerevisiae strain bearing the Sp6 cDNA and the human Hs10 beta cDNA was also viable. No interspecific complementation was observed for the human hRPB25 (Hs5) homolog of the yeast ABC27 (Sc5) subunit.

Synthesis and maturation of viral transcripts in herpes simplex virus type 1 infected HeLa cells: the role of interchromatin granules

The response of the cellular RNA processing machinery to herpes simplex virus type 1 (HSV-1) infection was studied at the ultrastructural level in HeLa cells and compared to the distribution of RNA polymerase II molecules and viral RNA. Immunogold labeling of RNA polymerase II molecules revealed that viral genome transcription was restricted to filaments in an intranuclear, virus-induced region. This region also contained viral RNAs as revealed by in situ hybridization of two biotinylated viral DNA probes: a probe encompassing a limited portion of the viral genome (the F fragment) and a probe for the total genome. In addition, the latter probe revealed large amounts of viral RNA within the clusters of interchromatin granules, intranuclear structures of normal cells that became enlarged during HSV-1 infection. Components of spliceosomes were localized by in situ hybridization with biotinylated U1 and U2 DNA probes. The large viral region contained only traces of U1 and U2 RNAs, probably because of the low frequency of splices of viral transcripts. The clusters of interchromatin granules, however, accumulated U1 and U2 RNAs with the same frequency as in noninfected cells. Poly(A) RNA was detected by in situ hybridization of a biotinylated poly(dT) probe. Some was present over the filaments of the virus-induced region but most was accumulated in the clusters of interchromatin granules. Our data suggest, therefore, that the clusters of interchromatin granules, in addition to their involvement in spliceosome component assembly, might also be a transient storage site for some families of viral mRNA, possibly a sorting site that regulates their migration.

Chromosomal localization of human RNA polymerase II subunit genes

The eukaryotic DNA-dependent RNA polymerase II (or B) is composed of 10 to 14 polypeptides ranging from 220 to 10 kDa. To gain further insight into the molecular structure and function of these subunits, we have undertaken the molecular cloning of nucleotide sequences corresponding to the human enzyme. The cDNAs of five subunits (hRPB220, hRPB140, hRPB33, hRPB25, and hRPB14.5) have been isolated. Using in situ hybridization, we show that the genes of these subunits have distinct chromosomal locations (17p13, 4q12, 16q13-q21, 19p13.3, and 19q12, respectively). Thus, if assembly of active polymerase molecules requires coordinated expression from these independent genes, mechanisms that ensure tight coregulation of the corresponding promoters must exist.

A 14.4 KDa acidic subunit of human RNA polymerase II with a putative leucine-zipper

The cDNA of a small subunit (hRPB14.4) of RNA polymerase II (or B) from HeLa cells has been cloned. A 127 residue peptide sequence (calculated molecular weight of 14,478; isoelectric point of 3.7) was deduced and compared to that of the homologous subunit of Saccharomyces cerevisiae polymerase (ABC23, encoded by the RPB6/RPO26 gene). About 50% of the total residues were found to be conserved between yeast and man, with the C-terminal two-third being the most conserved (72% identity). A putative leucine-zipper comprising four properly spaced leucine residues, but not preceded by a basic domain, was identified near the C-terminal end of both proteins.

Structure of the gene encoding the 14.5 kDa subunit of human RNA polymerase II

The structure of the gene encoding the 14.5 kDa subunit of the human RNA polymerase II (or B) has been elucidated. The gene consists of six exons, ranging from 52 to over 101 bp, interspaced with five introns ranging from 84 to 246 bp. It is transcribed into three major RNA species, present at low abundance in exponentially growing HeLa cells. The corresponding messenger RNAs contain the same open reading frame encoding a 125 amino acid residue protein, with a calculated molecular weight of 14,523 Da. This protein (named hRPB14.5) shares strong homologies with the homologous polymerase subunits encoded by the Drosophila (RpII15) and yeast (RPB9) genes. Cysteines characteristic of two zinc fingers are conserved in all three corresponding sequences and, like the yeast protein, the hRPB14.5 subunit exhibits zinc-binding activity.

[Cytomegalovirus arteriolitis: gangrene of the feet and early coronary disease after heart transplantation]

Peripheral arteriolitis of the legs from the 4th postoperative day after cardiac transplantation caused ischemia of the feet and required bilateral transmetatarsal amputations on the 28th postoperative day. The causal condition was cytomegalovirus infection, confirmed by rising IgM antibody titres, the detection of a viraemia on the 33rd postoperative day, and, above all, the presence of cytomegalic inclusion bodies in many endothelial arteriolar cells of the amputated limbs. The patient died four months after transplantation and autopsy revealed major lesions in all the distal coronary vessels of the graft which occluded over 4/5ths of the coronary lumens. An aspergillus septicemia was the direct cause of death.

[Evaluation of non invasive methods for the diagnosis of atherosclerosis of the graft after orthotopic cardiac transplantation]

The frequency and severity of atherosclerosis of the cardiac transplant make it an essential complication of cardiac transplantation. Coronary angiography is the usual diagnostic method but it has severe limitations. In order to evaluate other diagnostic methods coronary angiography and non-invasive techniques: echocardiography, exercise stress ECG, exercise radionuclide ejection fraction, stress Thallium scintigraphy, were performed practically simultaneously in 60 patients after cardiac transplantation. These non-invasive methods were said to be positive in the presence of, respectively, a segmental wall motion abnormality, ischaemic ST segment depression, absence of increased ejection fraction on exercise, reversible or irreversible myocardial hypofixation. Coronary angiography was considered as the reference procedure for distinction between "normal coronary circulation" (no angiographically detectable lesion) and "graft atherosclerosis" (at least one coronary stenosis irrespective of the severity and extension). None of the non-invasive methods had an adequate sensibility when compared with coronary angiography (echocardiography 0.27, exercise stress ECG 0.28, exercise radionuclide ejection fraction 0.64, myocardial scintigraphy 0.62) or negative predictive value (echocardiography 0.56, exercise stress ECG 0.58, exercise radionuclide ejection fraction 0.68, myocardial scintigraphy 0.66). This inadequacy of the non-invasive technique may be explained by the fact that they are more adapted to the diagnosis of myocardial ischaemia than that of coronary studies. In addition, the extent of the coronary lesions may have masked discordance between 2 segments by the global hypovascularisation. The results of this study indicate that the non-invasive methods studied cannot be recommended for diagnosis of atherosclerosis of cardiac transplants.

Primary structure of the second largest subunit of human RNA polymerase II (or B)

The cDNA of the second largest subunit of RNA polymerase II (or B) from HeLa cells has been cloned and sequenced. A predicted amino acid sequence of 1174 residues (calculated molecular mass of 133,896 Da) was derived from the longest open reading frame and compared to the sequences of homologous subunits of polymerases of eukaryotic, archaeal and bacterial origin. After optimal alignment, about 16% of the residues were found to be conserved throughout evolution, from human to Escherichia coli. About 2/3 of the overall length of the conserved domains delineated by these residues are clustered within the C-terminal half of the human polypeptide, whereas the remaining is spread over its N-terminal half. The putative functional significance of these conserved domains is discussed.

[Causes of failure analysis after cardiac transplantation. From a consecutive series of 91 cases]

Ninety-three cardiac transplantations were carried out in 91 patients (2 retransplantations) between March 1st 1987 and November 1st 1989, in 84 adults and 7 children under 15 years of age. The indications were dilated cardiomyopathy (48%), ischemic cardiomyopathy (35%), decompensated valvular heart disease (11%), congenital heart disease (3%) and two cases of Uhl's anomaly. Twelve patients underwent transplantation after external circulatory assistance (13%), 11 patients after inscription on the list of extreme emergencies, and 68 on an elective basis (74%). The postoperative immunosuppressive protocol was triple therapy: Ciclosporine, Azathioprine and Prednisone. Three of the children died. The early adult mortality was 9 cases (10.7%). It was 8% in patients operated electively. Major infectious complications occurred in 10 patients (11%). Rejection was looked for by systematic endomyocardial biopsy and echocardiography. Three hundred and forty-nine biopsies were made. Thirty-five patients (44%) had no problems of rejection. Seventy-nine patients have now been followed up for an average of 19 months. There were 7 late deaths. Seventy seven per cent of the survivors are asymptomatic. Acute rejection and transplant dysfunction were the two main causes of early mortality after cardiac transplantation. Although the long-term prognosis is uncertain, the medium-term results are very encouraging.

[Saint-Jude Medical tricuspid prosthesis. Long-term clinical, biological and echocardiographic assessment]

Twenty-four patients with a Saint-Jude Medical tricuspid valve prosthesis, aged 5 to 77 years, were studied. The etiology of the tricuspid lesion was rhumatic in 17 cases, infectious in 4 cases, and congenital in the other 3. Fourteen patient (58%) had undergone previous valve surgery, 7 of whom had undergone tricuspid valve replacement (TVR) by a bioprosthesis. Three patients were operated on for the third time. The TVR was isolated (4 cases) or associated with aortic valve replacement (3 cases), mitral valve replacement (8 cases), double aortic and mitral valve replacement (7 cases), repair of a ventricular septal defect (VSD) (1 case) and radical treatment of a Wolff-Parkinson-White syndrome (WPW) in 1 case. There were 3 early deaths (12.5%). Eighteen of the 21 survivors were followed up clinically, biologically (detection of hemolysis) and by Doppler echocardiography for an average period of 45 months (range 10 to 96 months). The clinical benefit was clear cut. No embolic complications were observed and there were no cases of hemolysis. The mean resting tricuspid pressure gradient was 3.57 +/- 2.36 mmHg. The Saint-Jude Medical prosthesis would therefore seem to be a good alternative to other mechanical valve prosthesis in the tricuspid position and without the risk of valve degeneration associated with bioprosthesis.

[Abnormal origin of the left coronary artery in the adult. Scintigraphic and surgical correlations]

The authors report two cases of anomalous origin of the left coronary artery from the pulmonary artery in the adult. The two patients were pauci-symptomatic and were successfully operated, the one by reimplantation of the left coronary artery in the aorta and the other by an internal mammary artery left anterior descending artery bypass. Resting and stress myocardial scintigraphy and radionuclide ventriculography were performed before and after surgery in both cases. An analysis of segmental wall motion was possible in one patient. Before surgery, there was hypo-fixation of the tracer during the stress test and an alteration of left ventricular function. Postoperative isotopic investigations confirmed the efficacy of surgery the absence of regional ischemia and the normalisation of the ventricular contraction. These results argue in favour of a surgical reconstruction of a two coronary system, given the spontaneous risk of sudden death in this condition.

[Assisted circulation by external heterotopic prosthesis as a bridge to heart transplantation]

Eleven patients aged 7 to 58 years were placed on assisted circulation with Pierce (2 cases) or Abiomed (9 cases) external prosthetic ventricles as a bridge to cardiac transplantation. The indications were terminal cardiac failure following cardiomyopathy (7 cases), decompensated ischemic heart disease (3 cases) and subacute post-transplantation rejection (1 case). The duration of the assisted circulation ranged from 24 hours to 11 days. All patients were transplanted but 3 died after transplantation (27%). The circulatory assistance was satisfactory in all patients as shown by the regression of clinical signs of low cardiac output and the normalisation of diuresis. The complications observed during assisted circulation and after cardiac transplantation were: haemorrhage (36%), infection (27%) and thromboembolism (9%). These preliminary results with a 72% post-transplantation survival rate, show that both systems are effective "bridges to cardiac transplantation". The Abiomen device is excellent value for money and relatively simple to install and represents a good compromise between the sophisticated techniques of circulatory assistance and the problems of the cost of health care.

Use of the Abiomed BVS System 5000 as a bridge to cardiac transplantation

The Abiomed BVS System 5000 (Abiomed Cardiovascular, Inc., Danvers, Mass.) is a gravity-filled, pneumatically driven external prosthetic ventricle that has been implanted as a circulatory support device in six patients 9 to 58 years of age, presenting with a refractory heart failure nonamenable to any type of corrective operation. Three (including a 9-year-old girl) had an end-stage nonobstructive myocardiopathy, and two (including one patient who had had a massive recent myocardial infarction) had an ischemic heart disease. When first seen, the 58-year-old patient had an acute rejection and graft failure occurring 2 months after a first transplantation. All patients showed evidence of a low-output state (cardiac index less than 1.5 L/min/m2), with renal failure (mean urinary output, less than 27 ml/min) and hypoxia (mean arterial oxygen pressure = 56 torr under 80% forced inspiratory oxygen), despite maximum pharmacologic support (dobutamine, 16 to 18 gamma/kg/min; dopamine, 3 to 18 gamma/kg/min; adrenaline, 0.2 to 0.7 gamma/kg/min; furosemide, 7 to 17 gamma/kg/min). The device was implanted through a midline sternotomy and under peripheral normothermic bypass. Five patients received a biventricular support, and one a single left prosthetic ventricle. The cannulation included a right-angled cannula in both the left and right atrium and a suture of the arterial Dacron tubes onto the ascending aorta and main pulmonary artery. After careful deairing of the tubing and ventricles, the console was activated and the bypass progressively discontinued. Heparin infusion was begun 3 hours after chest closure and was continued for the duration of assist pumping, which was 2 to 11 days (mean duration, 7.43 days). The system could provide a complete support of the circulation with both right and left ventricular index remaining stable at 2.4 to 3 L/min/m2. After a dramatic improvement at the time of the system activation, the urinary output remained adequate, thus allowing for a decreasing need for diuretic therapy. In two cases, including one of isolated left ventricular assist pumping, the circulation could be totally supported during 11 hours and 23 hours, respectively, of refractory ventricular tachycardia. Four of six patients were shortly weaned from inotropic agents. Hematologic studies showed a moderate decrease of the coagulation factors level during the first 6 hours of circulatory support, and this remained stable and within normal limits thereafter. There have been three cases of bleeding complications necessitating surgical revision on the sixth hour, the twelfth hour, and the sixth day, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

[Treatment of ventriculo-pulmonary disconnections with prosthetic conduits. Long-term results]

Between 1973 and 1989, 81 consecutive patients aged 2 to 42 years old, with ventriculo-pulmonary discontinuity, were treated by implantation of prosthetic conduits. The initial pathology was Tetralogy of Fallot (33%), complete transposition of the great arteries (20%), truncus arteriosus (17%), double outlet right ventricle (17%) and atrioventricular discordance with L malposition of the great arteries (10%). The overall early mortality was 22% (18 cases) and 14% (5 cases) in the 36 patients operated after 1982. Sixty three patients were followed up for 3 months to 16 years; there were 8 late deaths which occurred spontaneously or at reoperation. Postoperative catheterisation was carried out in 33 cases; the average ventriculopulmonary systolic pressure gradient was 40 +/- 26 mmHg. Six patients were reoperated to change the conduit, on average 6 years +/- 23 months after the first operation. Five other patients underwent endoluminal dilatation of a stenosed conduit which delayed reoperation to change the conduit in 3 cases. Prosthetic conduits have been extensively used in patients with ventriculo-pulmonary discontinuity because they are readily available. However, because of progressive degradation of the prostheses between the 5th and 10th postoperative years, other therapeutic solutions should be considered, i.e. endoventricular repair when possible and, in other cases, the use of aortic homografts.

[Apico-aortic shunts. Indications, results]

Seven children or adolescents aged 8 to 20 years (average 13.5 years) underwent implantation of an apico-aortic conduit from 1980 to June 1989. Eleven previous operations under cardiopulmonary bypass had been performed. The indications were recurrence of muscular subaortic stenosis and/or congenital valvular stenosis in 3 cases, and stenotic, previously implanted aortic valve prosthesis of small calibre in 4 cases. The preoperative left ventricular-aortic systolic pressure gradient was between 70 and 130 mmHg. The first two patients had a bioprosthetic valvulation and the 5 succeeding patients a St Jude Medical mechanical prosthesis. The early and late mortality was nil. The average follow-up period is 5, 6 years at present (range 6 months to 9 years). One patient had to undergo repeat valve replacement after 5 years for degenerescence of the porcine bioprosthesis implanted in the conduit. No other complications related to the conduit or valve were observed. At the endpoint of the study all patients were asymptomatic without treatment. Control echocardiographic data showed normalisation of the indices of left ventricular function. Apico-aortic conduits would seem to be a safe and effective technique for the treatment of recurrent severe obstruction of the left ventricular outflow tract.

The segment-specific gene Krox-20 encodes a transcription factor with binding sites in the promoter region of the Hox-1.4 gene

Krox-20 is a mouse zinc finger gene expressed in a segment-specific manner in the early central nervous system, which makes it a potential developmental control gene. In this report, we show that the Krox-20 protein binds in vitro to two specific DNA sites located upstream from the homeobox containing gene Hox-1.4. The nucleotide sequence recognized by Krox-20 is closely related to the Sp1 target sequence, which is consistent with the similarity existing between the zinc fingers of the two proteins. In co-transfection experiments in cultured cells, Krox-20 dramatically activates transcription from the herpes simplex virus thymidine kinase promoter when an oligomer of its binding site is present in cis close to the promoter. Analysis of mutated binding sites demonstrates that the level of activation by Krox-20 correlates with the affinity of the protein for the mutant sequence. These data indicate that Krox-20 constitutes a sequence-specific DNA-binding transcription factor. Parallel analysis of the expression of Krox-20 and Hox-1.4 in the neural tube by in situ hybridization revealed no overlap, arguing against direct interactions between these two genes. The possible involvement of Krox-20 in the regulation of the transcription of other homeobox genes is discussed in view of their respective patterns of expression.

[Total anomalous pulmonary venous connection. Results of repair in 50 infants]

Fifty infants with isolated total anomalous pulmonary venous connection (TAPVC) were operated between 1/01/73 and 31/12/87. The average weight at surgery, which was performed under hypothermia with circulatory arrest in 92 per cent of cases, was 4.5 Kg. The preoperative pulmonary to systemic pressure ratios (PAP/PS) enabled identification of two groups of patients: Group I: TAPVC without severe pulmonary hypertension (PAP/PS less than 0.85) (n = 35), and Group II: TAPVC with severe pulmonary hypertension (PAP/PS greater than 0.55) (n = 15). The hospital mortality was 22 per cent (8 cases) in Group I compared with 73 per cent (11 cases) in Group II (p less than 0.05). Patients in Group II were younger (64 days compared with 137 days, p less than 0.02), lighter (p less than 0.05) and had preoperative mean pulmonary artery systolic pressures of 83 mmHg (p greater than 0.001). Three patients in Group I required early reoperation for stenosis of the pulmonary veins at the site of repair resulting in pulmonary hypertension, and all died. The global survival was 28 patients with an average follow-up of 7 years (range 1 to 15 years). Six of these patients were reoperated (2 phrenoplications, 4 atrial shunts). All survivors are asymptomatic and have no conduction defects. Control echocardiography in 15 of the 28 survivors was judged to be normal. These results show that obstructive forms of TAPVC (Group II) carry a very poor prognosis: immediate results in this group could only be improved by earlier surgery. The clinical long-term results in those who survive surgery are very satisfactory.

The SV40 TC-II(kappa B) enhanson binds ubiquitous and cell type specifically inducible nuclear proteins from lymphoid and non-lymphoid cell lines

We have characterized the complexes resulting from the specific binding in vitro of proteins present in nuclear extracts of several lymphoid and non-lymphoid cell lines to the TC-I and TC-II sequences of the simian virus 40 (SV40) enhancer. No proteins could be detected, binding selectively to the TC-I sequence, but two proteins TC-IIA and TC-IIB were identified interacting specifically with both the TC-II/kappa B enhanson, 5'-GGAAAGTCCCC-3' (important for the activity of the SV40 enhancer in vivo), and with the related H-2Kb enhanson, 5'-TGGGGATTCCCCA-3'. The binding of these two proteins to mutated TC-II enhansons correlates with the effect of these mutations in vivo, suggesting that both proteins may be important for SV40 enhancer activity. The TC-IIA binding activity was present in nuclear extracts of mature lymphoid B cells and was increased in pre-B cell nuclear extracts by lipopolysaccharide (LPS) and cycloheximide treatment. Furthermore, complex formation between the TC-IIA protein and the TC-II enhanson was efficiently competed by the kappa B motif from the kappa chain enhancer, indicating that TC-IIA is the NF-kappa B factor or a closely related protein. However, in contrast to previous reports, a TC-IIA/NF-kappa B-like protein whose properties could not be distinguished from those of the TC-IIA protein present in lymphoid B cells, was found in nuclear extracts of several untreated non-lymphoid cell lines, notably of HeLa cells, but not of undifferentiated F9 embryonal carcinoma (EC) cells [F9(ND)]. The TC-IIA binding activity which was moderately increased in HeLa cell nuclear extracts by 12-O-tetradecanoylphorbol-13-acetate (TPA) and/or cycloheximide treatment could be induced in nuclear extracts of F9(ND) cells by cycloheximide, but not by TPA. Moreover, the TC-IIA binding activity could be induced in cytosolic fractions from F9(ND) cells by treatment with deoxycholate, indicating that these cells contain an inhibitor protein similar to the previously described NF-kappa B inhibitor, I kappa B. The second TC-II enhanson binding protein, TC-IIB, which could be clearly distinguished from the TC-IIA/NF-kappa B-like protein, by a number of differential properties, resembles the previously described KBF1/H2TF1 protein as it binds with a higher affinity to the H-2Kb enhanson than to the TC-II/kappa B enhanson, and its pattern of methylation interference on the H-2Kb and TC-II/kappa B enhansons is identical to that reported for the KBF1/H2TF1 protein.(ABSTRACT TRUNCATED AT 400 WORDS)

The mouse Hox-1.4 gene: primary structure, evidence for promoter activity and expression during development

This study reports the structure of the mouse homeobox-containing gene Hox-1.4 of the HOX-1 cluster, as well as its expression pattern during embryonic and fetal development. The overall structure of this gene includes two major exons, the second of which encodes the homeo-domain. The putative Hox-1.4 protein displays similarities with products of homologous genes located at the same relative positions in other HOX clusters. A fragment extending 360 base pairs (bp) upstream of a transcriptional start site was shown to be able to promote transcription in transfected cells. This fragment is GC-rich and contains binding sites for the Sp1 transcription factor. In situ hybridization studies revealed the Hox-1.4 expression pattern during development. As already reported for several other murine Hox genes, Hox-1.4 is expressed in the fetal central nervous system (CNS), in structures derived from somitic mesodermal condensations (sclerotomes, prevertebrae) as well as in several mesodermal components of various organs and structures such as lungs, gut, stomach, intestine and meso- and metanephros. This expression pattern is in good agreement with recent proposals concerning the involvement of such genes in the establishment of the vertebrate body plan as well as the relationship between the positions of these genes within their clusters and the anteroposterior restriction of their expression domains.

[Technic for implanting biventricular external assistance devices. Pending cardiac transplantation]

The extensive development of orthotopic heart transplantation results in a relative shortage of grafts. When cardiac grafts are unavailable, some patients at the end-stage of decompensated heart failure may benefit from a biventricular external circulatory assistance device as a "bridge" to transplantation. We describe a reproducible technique for the implantation of such external devices, based on the systematic use of extracorporeal circulation. This technique was tested in 8 patients. Its main advantage is that it prevents thromboembolic complications which are a constant threat when the devices are used for a prolonged period.

[Surgical treatment of complete atrioventricular canal. Value of the "composite double patch" technic]

Between January 1, 1982 and January 1, 1988, 49 complete corrections of complete atrioventricular canal were performed in children aged from 4 months to 8 years. 41 were infants less than 2 years' old and 31 were less than one year old. In the last 35 patients the "composite double patch" technique was used, consisting of closure of the interventricular septal defect with a dacron patch, followed by closure of the ostium primum with a pericardial patch. The mitral cleft was left intact in the last 6 operations. The overall mortality rate was 35 p. 100 (17 patients). It was 23 p. 100 in infants under 1 year and 17 p. 100 in infants aged from 6 to 12 months at the time of surgery (p less than 0.01). Seven of the 35 children in whom the "composite double patch" technique was used died (20 p. 100). Only one early death was recorded among the last 15 children operated upon. Two reoperations were performed: one within one month of the first operation, the other 4 months later for residual mitral regurgitation with haemolysis. 32 children were followed up for periods of 2 months to 6 years, 10 of them for more than 3 years. Two late deaths occurred during the follow-up. Grade 2 or 3/4 residual regurgitation was found in 14 patients who have regular clinical and echocardiographic examinations.(ABSTRACT TRUNCATED AT 250 WORDS)

[Surgery of the thoracic aorta. Value of tissucol]

The techniques for sealing with the Tissucol fibrin glue, used in repair of aortic dissections and aneurysms, are described. We applied this method to 24 patients operated upon for acute (9 cases) or chronic (15 cases) lesions of the thoracic aorta. No patients died of haemorrhage, and post-operative bleeding was only 500 ml on average. Provided strict precautions are taken, this adjuvant haemostatic method considerably improves the immediate prognosis of acquired aortic lesions. Other operations of cardiac surgery may benefit from these sealing techniques the cost of which must be weighed against the blood transfusion units that are saved.

Constitutive expression of (2'-5') oligo A synthetase confers resistance to picornavirus infection

Study of the mechanisms by which interferon (IFN) treatment of cells induces resistance to virus infections has been complicated by the multiple biochemical changes induced. Over 20 proteins are increased by IFN, including the double-stranded (ds) RNA-activated protein kinase, (2'-5') oligo A synthetase, surface proteins such as the major histocompatibility complex (MHC) proteins, and various proteins with unknown functions. The availability of cloned complementary DNAs for several IFN-induced proteins now allows us to probe their roles in IFN action. For instance, the murine Mx protein has been shown to confer resistance, to influenza virus. We studied chinese hamster ovary (CHO) cell clones expressing high constitutive levels of (2'-5') A synthetase as a result of transfection with the cDNA encoding the enzyme form which has a relative molecular mass (Mr) of 40K. Elevated enzyme correlates directly with resistance to infection by a picornavirus such as Mengo, but does not make the cells resistant to vesicular stomatitis virus (VSV).

Interferon-responsive regulatory elements in the promoter of the human 2',5'-oligo(A) synthetase gene

The interferon (IFN)-activated human 2',5'-oligo(A) synthetase E gene contains 11 RNA starts and lacks TATA and CAAT signals. DNA sequences around the promoter make the expression of the chloramphenicol acetyltransferase gene (CAT) inducible over 20-fold by IFN. A 72-base-pair segment (E-IRS) immediately upstream of the RNA starts was defined as being required for IFN-activated expression of the E-gene promoter-CAT constructs and acts in a position-independent manner. It also confers IFN-activated enhancement to the herpes simplex virus thymidine kinase promoter. On this promoter, the 5' part of the E-IRS functions as a constitutive enhancer, while the last 16 base pairs of the E-IRS is sufficient to give IFN-induced expression. On the E-gene promoter, the constitutive enhancer and the IFN-activated sequence are both needed but can be separated. In addition, promoter competition experiments indicate a third regulatory region which helps to repress expression of the E gene in uninduced cells.

One cell-specific and three ubiquitous nuclear proteins bind in vitro to overlapping motifs in the domain B1 of the SV40 enhancer

We have used the gel retardation assay to investigate the binding of nuclear proteins to the domain B1 of the SV40 enhancer, which contains the GT-II motif. Four proteins (GT-IIA, GT-IIB alpha, GT-IIB beta and GT-IIC) were detected, three of which were present in nuclear extracts from several cell lines. The fourth protein (GT-IIC) showed a clear cell-specificity, being absent from the lymphoid cell extracts tested. The results of methylation interference assays and of the binding of the proteins to mutated templates indicate that the domain B1 contains three distinct, but overlapping, protein-binding motifs (GT-IIA, B and C). The cell-specific binding of protein GT-IIC in vitro correlates with the in vivo enhancer activity of its cognate motif, strongly suggesting that this protein acts as a positive trans-acting enhancer factor. Two of the proteins also recognize other enhancer motifs; protein GT-IIB alpha binds to the microE3 motif present in the immunoglobulin heavy chain enhancer; protein GT-IIC binds to an enhancer motif of the polyomavirus mutant PyEC9.1 adapted to growth in F9 embryonal carcinoma cells, but not to the corresponding wild-type sequence.

In vitro binding of several cell-specific and ubiquitous nuclear proteins to the GT-I motif of the SV40 enhancer

We have investigated the specific in vitro binding of nuclear proteins from several cell lines to the GT-I motif of the SV40 enhancer which overlaps with the canonical enhancer "core" homology. The binding of three proteins (GT-IA, GT-IB, and GT-IC), one of which (GT-IC) exhibits cell specificity, was detected. Competition and direct binding experiments demonstrated that the two ubiquitous proteins also bind to the GC-rich motif III from the 21-bp repeat upstream element of the SV40 early promoter and that protein GT-IA is most probably the transcription factor Sp1. The third, cell-specific protein GT-IC exhibited a high affinity for both the GT-I motif and an upstream element in the promoter of the mouse beta-major-globin gene, suggesting that this protein can act both as an enhancer and an upstream element trans-acting factor. The good correlation between the known cell-specific in vivo activity of the wild-type and mutated GT-I motif and the cell-specific binding of protein GT-IC in vitro strongly supports the conclusion that this protein is an enhancer factor. Interestingly, its cognate recognition sequence does not coincide with the core homology.

In vitro binding of cell-specific and ubiquitous nuclear proteins to the octamer motif of the SV40 enhancer and related motifs present in other promoters and enhancers

We have used the gel retardation and DNase I footprinting assays to investigate the in vitro binding of nuclear proteins to the octamer motif present in domain A of the SV40 enhancer and in other enhancer and promoter elements. Three apparently cell-specific (oct-B1A, oct-B1B and oct-B2) and one ubiquitous (oct-B3) proteins were detected in various lymphoid and non-lymphoid cell extracts. We show that the previously described 'ubiquitous' NF-A1 factor may correspond in fact to two proteins, oct-B1A in HeLa cells and oct-B1B in lymphoid cells. Interestingly, the HeLa cell protein oct-B1A formed a complex with the SV40 octamer, which could be detected in gel retardation, but not in DNase I footprinting assays. This absence of protection from DNase I digestion correlates with the inactivity of the SV40 octamer in HeLa cells in vivo. We have also found that the in vitro interaction between the SV40 octamer motif and the lymphoid cell-specific protein oct-B2 was negatively modulated by a component present in the nuclear extracts from several lymphoid cell lines. The interactions between the multiple octamer-binding proteins and the related octamer motifs present in other promoter and enhancer elements were systematically compared and the possible role of these proteins in the control of transcription is discussed.

Efficient constitutive production of human IFN-gamma in Chinese hamster ovary cells

A human genomic DNA segment of 5.6 kb containing the entire gene for immune interferon-gamma was fused through its 5'-untranslated region to the corresponding region of the simian virus 40 (SV40) T-antigen gene. The SV40 early promoter used contained a modified transcriptional enhancer element with a 93-bp repeat. Supercoiled plasmid DNA was used to transfect Chinese hamster ovary (CHO) cells, the selectable marker being a SV40-dihydrofolate gene construct. Constitutive expression of the IFN-gamma gene in primary transformants was high, especially if a Harvey murine sarcoma virus long terminal repeat (LTR) was present in addition to the SV40 promoter. After gene amplification by methotrexate selection, CHO-gamma cell lines were obtained that produce 1.5-2 million units of IFN-gamma per million cells and per day (200,000 molecules per cell per minute). Metabolic labeling showed that over 90% of the protein secreted by such cells is human IFN-gamma. A one-step immuno-affinity chromatography on monoclonal antibodies yielded pure IFN-gamma with 1-2 X 10(8) units/mg protein. Like IFN-gamma from human white blood cells, the IFN-gamma from CHO-gamma cells is a mixture of two glycoproteins of 26,000 and 20,000 daltons with traces of the unglycosylated 17,000-dalton polypeptide. Large-scale cultures in 1% serum routinely yield over 600,000 units of human IFN-gamma/ml culture per day.

Requirement of stereospecific alignments for initiation from the simian virus 40 early promoter

The distance between the simian virus 40 early promoter elements has been altered by inserting either odd or even multiples of half a DNA turn. There are marked differences in the in vivo effects of these two types of insertions on initiation of transcription from this promoter.

All six GC-motifs of the SV40 early upstream element contribute to promoter activity in vivo and in vitro

Recombinants in which the six GC-motifs (I-VI) present in the upstream element of the SV40 early promoter region have been point mutated either individually or in pairs were used to determine the possible contribution of each GC-motif to the function of the overlapping early-early and late-early SV40 promoters. GC-motif I, and to a lesser extent, GC-motifs II and III, are critical for initiation at the early-early start sites. GC-motifs IV-VI play a subsidiary role. Mutations in GC-motifs I and II do not decrease the activity of the late-early promoter, whereas mutations in the GC-motifs III-VI have a moderate effect on it. The in vivo phenotype of the GC-motif mutants can be almost fully reproduced in vitro using a nuclear extract. DNase I protection footprinting experiments using wild-type or mutated templates and nuclear extracts indicate that each GC-motif behaves principally as an independent protein-binding site, presumably for transcription factor Sp1. The effect of changing the position of the 21-bp repeat region on initiation from the early-early and late-early start sites indicates that there is little flexibility in the position in which this upstream element can efficiently activate initiation of transcription from these start sites.

Effect of the 21-bp repeat upstream element on in vitro transcription from the early and late SV40 promoters

The role of the 21-bp repeat region [simian virus 40 (SV40) coordinates 40-103] on early and late SV40 promoter functions has been investigated in vitro using a variety of mutated templates. Using either a HeLa whole cell extract or a S100 extract, we analyzed the transcripts by quantitative S1 nuclease mapping. GC-rich motifs contained in the 21-bp direct repeat constituted an essential element for efficient early transcription in vitro in agreement with previous in vivo results. These GC-rich motifs act in a non-polar fashion, since inversion of the 21-bp region did not reduce early transcription. Some point mutations in the 22-bp imperfectly repeated sequence, that drastically reduce initiations from the early promoter in vivo, had little effect in vitro, indicating that all the functions of these GC-rich motifs cannot be reproduced in vitro at present. The requirement for the 21-bp repeat region was less stringent when the concentration of the early promoter sequence was increased, which suggests that its function may be to facilitate the recognition of the 'weak' SV40 early TATA box. The multiple late start sites were accurately used in vitro and the GC-rich motifs contained in the 21-bp repeat region were an important element for efficient in vitro initiation of transcription from the late promoter, irrespective of their orientation. However, the effect of the 21-bp repeat region on late initiations decreased strikingly with increasing distance to the start sites, although it was still detectable over a distance of 220 bp. Under the present in vitro conditions, the 72-bp repeat region stimulates weakly both early and late transcription.