DNA damage-binding proteins and heterogeneous nuclear ribonucleoprotein A1 function as constitutive KCS element components of the interferon-inducible RNA-dependent protein kinase promoter

Protein kinase regulated by RNA (PKR) plays important roles in many cellular processes including virus multiplication and cell growth, differentiation, and apoptosis. The promoter of the PKR gene possesses a novel 15-bp element designated KCS, positioned upstream of a consensus interferon (IFN)-stimulated response element, that is required for both basal and interferon-inducible transcription. Protein binding to the KCS element is not dependent upon IFN treatment and correlates with transcriptional activity of the PKR promoter. The identity of KCS-binding proteins (KBP) that selectively bind at the KCS element is largely unknown, except for the transcription factor Sp1. We now have purified KBP from HeLa cell nuclear extracts by ion-exchange and DNA-affinity chromatography steps and then identified four constituent proteins of the KBP complex by mass spectrometry and immunochemistry: KBP120 and KBP45 are the damaged DNA-binding protein subunits, p127 DDB1 and p48 DDB2, respectively; KBP100 is the transcription factor Sp1; and KBP35 is the heterogeneous nuclear ribonucleoprotein A1. The steady-state levels of these four KCS-binding proteins in human cells are not altered by IFN treatment. Components of the KBP complex bind selectively and constitutively to the KCS element in the absence of IFN treatment, both in vitro as measured by competition electrophoretic mobility shift assay (EMSA) and DNA pull-down assays and in vivo as measured by chromatin immunoprecipitation assays. Depletion of DDB2 by antisense strategy reduces KBP complex formation by EMSA. These results provide new insight into the biochemical identity and activity of proteins involved in PKR promoter function.

Functional analysis of the KCS-like element of the interferon-inducible RNA-specific adenosine deaminase ADAR1 promoter

The ADAR1 gene encodes an RNA-specific adenosine deaminase that alters the functional activity of both viral and cellular RNAs by posttranscriptional adenosine-to-inosine RNA editing. The interferon (IFN) responsive PI promoter of the ADAR1 gene possesses an IFN-stimulated response element (ISRE) responsible for IFN-inducibility, as well as an adjacent upstream sequence, designated kinase conserved sequence-like (KCS-l) element. The KCS-l element is similar to the 15-bp KCS element so far unique to the human and mouse RNA-dependent PKR kinase gene promoters. The KCS element of the PKR kinase (PKR) promoter is essential for both basal and IFN-inducible PKR promoter activity. We have now examined the functional properties of the KCS-l element of the ADAR1 PI promoter. Electrophoretic mobility shift assays (EMSAs) detected constitutively expressed nuclear proteins that bound selectively to the ADAR1 KCS-l element. Competition EMSA and antibody supershift assays indicated that ADAR1 KCS-l-binding proteins shared some properties with PKR KCS-binding proteins. However, transient transfection analyses performed with ADAR1 PI promoter constructs possessing deletion and substitution mutant forms of the KCS-l element revealed that the ADAR1 KCS-l element was not essential for either basal or IFN-inducible promoter activity. Substitution of the ADAR1 KCS-l element with the PKR KCS element increased both basal and inducible ADAR1 PI promoter activity. These results suggest that the KCS-l element of the ADAR1 PI promoter is not functionally equivalent to the KCS element of the PKR promoter.

The promoter-proximal KCS element of the PKR kinase gene enhances transcription irrespective of orientation and position relative to the ISRE element and is functionally distinct from the KCS-like element of the ADAR deaminase Promoter

The RNA-dependent protein kinase PKR promoter is interferon (IFN) inducible and possesses a novel 15-base pair (bp) constitutive activator element, designated kinase conserved sequence (KCS), in addition to an IFN-stimulated response element (ISRE). Deletion of the KCS element or point mutations within the KCS element greatly reduce both basal and IFN-inducible PKR promoter activity. The IFN-inducible RNA-specific adenosine deaminase ADAR1 promoter possesses a KCS-like (KCS-l) element. The sequences of the KCS and KCS-l elements and their positions relative to the cognate ISRE element are similar between the PKR and ADAR1 promoters. However, substitution of the ADAR1 KCS-l element for the KCS element of the PKR promoter resulted in significantly reduced basal and IFN-inducible promoter activities comparable to either point mutation or entire deletion of the PKR KCS element. The PKR KCS element selectively bound nuclear proteins more efficiently than did the ADAR1 KCS-l element. Reversing the positions of the KCS and ISRE elements of the PKR promoter relative to one another or reversing the orientation of either element while conserving the naturally occurring 4-bp spacing between the two elements did not significantly reduce basal or IFN-inducible promoter activity. Taken together, these results are consistent with the notion that the KCS and ISRE elements of the PKR promoter function as a unit.

The evaluation of a new intravascular blood gas monitoring system in the pig

OBJECTIVE

Our objective was to investigate the accuracy of a new intravascular blood gas sensor, the Paratrend 7 (P7) (Biomedical Sensors Ltd, Pfizer Hospital Products Group, High Wycombe, England) in a porcine model.

METHODS

A total of 12 sensors were inserted into 10 animals under total intravenous anesthesia. Changes in blood gas chemistry were produced over a wide range by manipulating the inspired oxygen and carbon dioxide concentrations and by adjustments in minute ventilation. Blood gas samples (BGA) were taken and analyzed during periods of stability; the results obtained were compared with the readings from the intravascular sensor.

RESULTS

A total of 292 blood gas samples were taken and analyzed for pHa, PaCO2, and Po2; the results were compared with the readings from the intravascular sensor. Correlation coefficients of r = 0.98 for PCO2 and r = 0.99 for PO2 were obtained. Analysis of bias and precision as mean +/- SD of the difference (P7 - BGA) gave the following results: pH bias = -0.03, precision = +/- 0.04; PCO2 bias = 0.65 mm Hg, precision = +/- 3.1 mm Hg; and PO2 bias = -6.50 mm Hg, precision = +/- 0.6 mm Hg. No problems with clot formation on the sensor were seen, and the sensors did not appear to show the "wall effect" seen with other systems.

CONCLUSIONS

The results obtained were well within the requirements for a clinically useful blood gas monitoring system.

Coronary vasoconstriction induced by vasopressin. Production of myocardial ischemia in dogs by constriction of nondiseased small vessels

BACKGROUND

We studied the effect of intracoronary administration of arginine-8-vasopressin on blood flow in nondiseased coronary arteries and determined whether this vasoconstriction was severe enough to produce ischemia in 30 dogs.

METHODS AND RESULTS

In group 1 (n = 6), after vasopressin administration coronary blood flow was decreased by 41% (p less than 0.002) without changes in heart rate or aortic pressure, and left ventricular ejection fraction measured by radionuclide angiocardiography was decreased by 18% (p less than 0.0005). In group 2 (n = 6), ischemia was confirmed by measurement of transmural pH changes. Administration of vasopressin decreased subendocardial pH of the infused zone from 7.40 +/- 0.03 to 7.31 +/- 0.07 (p less than 0.01). The subendocardial pH of the zone not infused with vasopressin did not change. To overcome the intrinsic regulation of blood flow, operating primarily in small coronary arteries, we hypothesized that vasopressin must increase resistance primarily in large rather than small coronary arteries. After intracoronary infusion in group 3 (n = 6), however, most (94%) of the increase in resistance during vasopressin administration was explained by an increase of resistance in small coronary arteries. In group 4 (n = 9), vasopressin decreased coronary blood flow by 50% and decreased local shortening by 90% at a time when systemic hemodynamics were unchanged. Coronary constriction induced by vasopressin, or the recovery from it, also was not altered by cyclooxygenase blockade.

CONCLUSIONS

Thus, vasopressin produces myocardial ischemia by constricting small, nondiseased coronary arteries severely enough to overcome the competition from normal coronary regulation, and this ischemic event is not mediated by prostaglandin products.

Noninvasive measurement of tissue carbon dioxide tension using a fiberoptic conjunctival sensor: effects of respiratory and metabolic alkalosis and acidosis

To evaluate potential clinical applications of a newly developed, noninvasive fiberoptic conjunctival carbon dioxide (PcjCO2) sensor designed to measure continuously tissue PCO2 in a vascular bed supplied by the internal carotid artery, we studied the effects of graded respiratory and metabolic alkalosis and acidosis on PcjCO2 in a hemodynamically stable canine model. Respiratory changes were induced by varying the frequency of ventilation and metabolic changes were induced by incremental infusions of sodium bicarbonate and hydrochloric acid. Continuous measurement of end-tidal carbon dioxide tension (PETCO2) was also performed. During respiratory alkalosis and acidosis, PcjCO2 values correlated well with PaCO2 (r = 0.96, n = 106); linear regression analysis of PcjCO2 vs. PaCO2 produced a slope of 1.01 and a y-intercept of 3.94 over a PaCO2 range of 12 to 76 torr. The mean PcjCO2-PaCO2 gradient was 4 +/- 3 (SD) torr. PETCO2 values also correlated well with PaCO2 (r = 0.91), as well as with PcjCO2 values (r = 0.91). Both PcjCO2 and PETCO2 showed a much weaker correlation with PaCO2 during metabolic alkalosis and acidosis, partly because the variation in PaCO2 was less. Moreover, the PcjCO2-PaCO2 gradient increased during the metabolic portion of the study up to a mean of 10 +/- 8 (SD) torr during metabolic acidosis, implying a build-up and/or lack of washout of CO2 from the conjunctival tissues, despite the normal physiologic range of PaCO2 values. We conclude that in a hemodynamically stable canine model, PcjCO2 and PETCO2 values correlate well with PaCO2 during pure respiratory alkalosis and acidosis; the correlation weakens significantly, however, with metabolic alterations in tissue CO2 levels.