Neoadjuvant chemoradiotherapy versus neoadjuvant chemotherapy followed by minimally invasive esophagectomy for locally advanced esophageal squamous cell carcinoma: a prospective multicenter randomized clinical trial

BACKGROUND

Neoadjuvant therapy is recommended for locally advanced esophageal cancer, but the optimal strategy remains unclear. We aimed to evaluate the safety and efficacy of neoadjuvant chemoradiotherapy (nCRT) versus neoadjuvant chemotherapy (nCT) followed by minimally invasive esophagectomy (MIE) for locally advanced esophageal squamous cell carcinoma (ESCC).

PATIENTS AND METHODS

Eligible patients staged as cT3-4aN0-1M0 ESCC were randomly assigned (1 : 1) to the nCRT or nCT group stratified by age, cN stage, and centers. The chemotherapy, based on paclitaxel and cisplatin, was administered to both groups, while concurrent radiotherapy was added for the nCRT group; then MIE was carried out. The primary endpoint was 3-year overall survival. This study is registered with ClinicalTrials.gov (NCT03001596).

RESULTS

A total of 264 patients were eligible for the intention-to-treat analysis. By 30 November 2021, 121 deaths had occurred. The median follow-up was 43.9 months (interquartile range 36.6-49.3 months). The overall survival in the intention-to-treat population was comparable between the nCRT and nCT strategies [hazard ratio (HR) 0.82, 95% confidence interval (CI) 0.58-1.18; P = 0.28], with a 3-year survival rate of 64.1% (95% CI 56.4% to 72.9%) versus 54.9% (95% CI 47.0% to 64.2%), respectively. There were also no differences in progression-free survival (HR 0.83, 95% CI 0.59-1.16; P = 0.27) and recurrence-free survival (HR 1.07, 95% CI 0.71-1.60; P = 0.75), although the pathological complete response in the nCRT group (31/112, 27.7%) was significantly higher than that in the nCT group (3/104, 2.9%; P < 0.001). Besides, a trend of lower risk of recurrence was observed in the nCRT group (P = 0.063), while the recurrence pattern was similar (P = 0.802).

CONCLUSIONS

NCRT followed by MIE was not associated with significantly better overall survival than nCT among patients with cT3-4aN0-1M0 ESCC. The results underscore the pending issue of the best strategy of neoadjuvant therapy for locally advanced bulky ESCC.

The lipid components of high-density lipoproteins (HDL) are essential for the binding and transportation of antimicrobial peptides in human serum

Antimicrobial peptides (AMPs) have been developed for the treatment of bacterial infections, but their applications are limited to topical infections since they are sequestered and inhibited in serum. Here we have discovered that the inhibition of AMPs by human serum was mediated through high-density lipoproteins (HDL) which are known to remove cholesterol from peripheral tissues. The susceptibility of AMPs to HDL varied depending on the degree of hydrophobicity of AMPs and their binding affinities to HDL. The phospholipids, such as phosphatidylcholine, of HDL were essential for AMP-binding. The dynamic binding interactions between AMPs and HDL were mediated through the hydrophobic interactions rather than by ionic strength. Interestingly, some AMPs, such as SMAP29, dissociated from the AMP-HDL complex and translocated to bacteria upon contact, while some AMPs, such as LL37, remained in complex with HDL. These results suggest that HDL binds AMPs and facilitates the translocation of them to the bacteria.

Fetal bovine serum albumin inhibits antimicrobial peptide activity and binds drug only in complex with α1-antitrypsin

Several antimicrobial peptides (AMPs) have been developed for the treatment of infections caused by antibiotic-resistant microbes, but their applications are primarily limited to topical infections because in circulation they are bound and inhibited by serum proteins. Here we have found that some AMPs, such as TP4 from fish tilapia, and drugs, such as antipyretic ibuprofen, were bound by bovine serum albumin only in complex with α1-antitrypsin which is linked by disulfide bond. They existed in dimeric complex (2 albumin -2 α1-antitrypsin) in the bovine serum only at fetal stage, but not after birth. The hydrophobic residues of TP4 were responsible for its binding to the complex. Since bovine serum is a major supplement in most cell culture media, therefore the existence and depletion of active albumin/α1-antitrypsin complex are very important for the assay and production of biomolecules.

Inhibition of bacterial adherence to biomaterials by coating antimicrobial peptides with anionic surfactant

Medical devices are widely used in modern medicine, but their utilities are often limited by the biofilm formation of bacteria that are tolerant to most antibiotics. In this report, antimicrobial peptides (AMPs) were coated onto biomaterials by the aid of surfactant through hydrophobic interactions. To increase the coating efficiency, stability of AMPs in body fluids and spectrum of antimicrobial activity, pairs of AMPs were coated simultaneously onto various substrates, such as silicone, polyurethane and titanium, which are commonly used components of biomedical devices. These coated AMPs exhibited very low cytotoxicity and hemolytic activities because they were gradually released into urine or serum. The AMP pairs, such as T9W + SAAP159 and T9W + RRIKA, coated onto the silicone discs were able to inhibit in vitro bacterial adherence in urine. Most importantly, AMP pairs coated onto the silicone tubing by surfactant SDBS could prevent bacterial adherence to mouse bladder and the silicone tubing implanted within it. These results provide a promising approach towards circumventing urinary catheter-associated infections caused by bacterial adherence.

Low pretreatment PNI correlates with worse survival in patients with stage III/IV NSCLC who received chemotherapy

The aim of this study was to investigate the prognostic value of the prognostic nutritional index (PNI) on the long-term survival of non-small cell lung cancer (NSCLC) patients who received platinum-based chemotherapy. Data on nutritional parameters and clinicopathological characteristics [e.g., albumin, total protein, body mass index (BMI), eastern cooperative oncology group (ECOG) performance status, stage, pathology, treatment strategy] were analyzed and retrospectively correlated with overall survival (OS). The PNI was calculated based on the concentration of albumin and lymphocyte count [10 × albumin, (g/dl) + 0.005 × lymphocyte (count/mm3)]. A receiver operating characteristic curve (ROC) analysis was used to find the optimal cut-off value of PNI. Univariate and multivariate analyses were used to evaluate the prognostic value of PNI. A total of 186 patients met the inclusion criteria. The optimal cut-off value for PNI was 50.45. Compared with the parameters of the low PNI group (n=76), high PNI was significantly associated with adenocarcinoma type, stage III, better ECOG and comprehensive treatment modality. The univariate analysis demonstrated that OS was superior when PNI ≥50.45, albumin ≥35 g/l, platelet-lymphocyte ratio (PLR) ≥163 and ECOG <2, and when the patient received a comprehensive treatment modality. In the multivariate analysis, PNI, TNM stage and treatment strategy were identified as independent predictors of survival in this study. This retrospective study demonstrated that a low PNI was related to worse overall survival in patients with stage III/IV NSCLC who received platinum-based chemotherapy. These data provided a conceptual basis for further research on the clinical application of the PNI index for patients receiving chemotherapy for intermediate- and advanced-stage NSCLC.

Sarkosyl-Induced Helical Structure of an Antimicrobial Peptide GW-Q6 Plays an Essential Role in the Binding of Surface Receptor OprI in Pseudomonas aeruginosa

The emergence of antibiotic-resistant microbial strains has become a public health issue and there is an urgent need to develop new anti-infective molecules. Although natural antimicrobial peptides (AMPs) can exert bactericidal activities, they have not shown clinical efficacy. The limitations of native peptides may be overcome with rational design and synthesis. Here, we provide evidence that the bactericidal activity of a synthetic peptide, GW-Q6, against Pseudomonas aeruginosa is mediated through outer membrane protein OprI. Hyperpolarization/depolarization of membrane potential and increase of membrane permeability were observed after GW-Q6 treatment. Helical structure as well as hydrophobicity was induced by an amphipathic surfactant, sarkosyl, for binding to OprI and possible to membrane. NMR studies demonstrated GW-Q6 is an amphipathic α-helical structure in DPC micelles. The paramagnetic relaxation enhancement (PRE) approach revealed that GW-Q6 orients its α-helix segment (K7-K17) into DPC micelles. Additionally, this α-helix segment is critical for membrane permeabilization and antimicrobial activity. Moreover, residues K3, K7, and K14 could be critical for helical formation and membrane binding while residues Y19 and W20 for directing the C-terminus of the peptide to the surface of micelle. Taken together, our study provides mechanistic insights into the mode of action of the GW-Q6 peptide and suggests its applicability in modifying and developing potent AMPs as therapeutic agents.

Solution structure and base specificity of cytotoxic RC-RNase 2 from Rana catesbeiana

Cytotoxic ribonucleases found in the oocytes and early embryos of frogs with antitumor activity are well-documented. RC-RNase 2, a cytotoxic ribonuclease isolated from oocytes of bullfrog Rana catesbeiana, consists of 105 residues linked with 4 disulfide bridges and belongs to the bovine pancreatic ribonuclease (RNase A) superfamily. Among the RC-RNases, the base preference for RNase 2 is UpG but CpG for RC-RNase 4; while RC-RNase possesses the base specificity of both UpG and CpG. Interestingly, RC-RNase 2 or 4 has much lower catalytic activity but only three-fold less cytotoxicity than RC-RNase. Here, we report the NMR solution structure of rRC-RNase 2, comprising three alpha-helices and two sets of antiparallel beta-sheets. The differences of side-chain conformations of subsite residues among RNase A, RC-RNase, RC-RNase 4 and rRNase 2 are related to their distinct catalytic activities and base preferences. Furthermore, the substrate-related residues in the base specificity among native RC-RNases are derived using the chemical shift perturbation on ligand binding.

Sex hormone binding globulin and risk of breast cancer in postmenopausal women: a meta-analysis of prospective studies

Previous studies on the association between sex hormone binding globulin (SHBG) level and risk of breast cancer in postmenopausal women reported conflicting results. A meta-analysis of prospective studies was performed to evaluate the association between SHBG level and risk of breast cancer in postmenopausal women. Pubmed (1980 to July 2014) and EMBASE (1988 to July 2014) were searched for eligible studies. Eligible studies were prospective cohort or nested case-control studies on the association between SHBG level and risk of breast cancer in postmenopausal women. Meta-analysis using random-effects model was performed to calculate the pooled risk ratios (RRs) with 95% confidence intervals (95% CIs). Of 946 studies identified, 26 prospective studies from 21 publications were finally included in the meta-analysis. In postmenopausal women, the pooled RR for breast cancer comparing highest with lowest categories of SHBG was 0.64 (95% CI 0.57-0.72, p<0.001, I(2)=6.5%). The pooled RRs were not obviously altered in the sensitivity analyses and subgroup analyses. In cumulative meta-analysis, a more significant association between SHBG level and risk of breast cancer in postmenopausal women was observed as evidence accumulated by publication year. There was no obvious risk of publication bias. High SHBG level is significantly associated with decreased risk of breast cancer in postmenopausal women, and it's a protective factor of breast cancer in postmenopausal women.

Differential influences of gastric bypass and sleeve gastrectomy on plasma nesfatin-1 and obestatin levels in patients with type 2 diabetes mellitus

OBJECTIVE

The mechanisms by which bariatric surgeries, including gastric bypass (GB) and sleeve gastrectomy (SG), achieve remission of type 2 diabetes mellitus (T2DM) and sustained weight reduction are unknown. We hypothesized that the novel anorexic hormone nesfatin-1 and another new hormone obestatin might contribute to the marked improvement in glycemic homeostasis and weight loss in diabetics after GB and SG.

METHODS

A hospital-based, prospective study was conducted. Overnight fasting plasma concentrations of nesfatin-1 and obestatin were analyzed in T2DM patients before surgery, and at 3 and 12 months after laparoscopic GB (n =12) and SG (n = 6).

RESULTS

At 12 months, reductions of body mass index (BMI), fasting blood glucose, and glycated hemoglobin were similar between GB and SG groups (P all > 0.05). Plasma nesfatin-1 levels in patients undergoing GB or SG significantly decreased after surgeries (P both < 0.05). In contrast, plasma obestatin concentrations significantly increased in patients after SG (P < 0.05) but without any alteration after GB. The alterations of plasma nesfatin-1 were significantly and negatively associated with the reduction of fasting blood glucose (P <0.05) at 12 months after GB and SG. In the SG group, the reduction of nesfatin-1 significantly and positively correlated with the decrease of BMI (P < 0.05).

CONCLUSIONS

GB and SG produce differential influences with regards to circulating nesfatin-1 and obestatin levels in non-morbidly obese, T2DM patients. Circulating nesfatin-1 may modulate glucose homeostasis in two surgical procedures, and participate in regulating body weight in SG.

Identification of a novel antimicrobial peptide from human hepatitis B virus core protein arginine-rich domain (ARD)

The rise of multidrug-resistant (MDR) pathogens causes an increasing challenge to public health. Antimicrobial peptides are considered a possible solution to this problem. HBV core protein (HBc) contains an arginine-rich domain (ARD) at its C-terminus, which consists of 16 arginine residues separated into four clusters (ARD I to IV). In this study, we demonstrated that the peptide containing the full-length ARD I–IV (HBc147-183) has a broad-spectrum antimicrobial activity at micro-molar concentrations, including some MDR and colistin (polymyxin E)-resistant Acinetobacter baumannii. Furthermore, confocal fluorescence microscopy and SYTOX Green uptake assay indicated that this peptide killed Gram-negative and Gram-positive bacteria by membrane permeabilization or DNA binding. In addition, peptide ARD II–IV (HBc153-176) and ARD I–III (HBc147-167) were found to be necessary and sufficient for the activity against P. aeruginosa and K. peumoniae. The antimicrobial activity of HBc ARD peptides can be attenuated by the addition of LPS. HBc ARD peptide was shown to be capable of direct binding to the Lipid A of lipopolysaccharide (LPS) in several in vitro binding assays. Peptide ARD I–IV (HBc147-183) had no detectable cytotoxicity in various tissue culture systems and a mouse animal model. In the mouse model by intraperitoneal (i.p.) inoculation with Staphylococcus aureus, timely treatment by i.p. injection with ARD peptide resulted in 100-fold reduction of bacteria load in blood, liver and spleen, as well as 100% protection of inoculated animals from death. If peptide was injected when bacterial load in the blood reached its peak, the protection rate dropped to 40%. Similar results were observed in K. peumoniae using an IVIS imaging system. The finding of anti-microbial HBc ARD is discussed in the context of commensal gut microbiota, development of intrahepatic anti-viral immunity and establishment of chronic infection with HBV. Our current results suggested that HBc ARD could be a new promising antimicrobial peptide.

Antibiotics-resistant pathogens have been a major problem to our public health. Recently, in our studies of human hepatitis B virus (HBV), we accidentally discovered potent and broad spectrum antimicrobial peptides from HBV core protein (HBc) arginine-rich domain (ARD). The peptides are mainly composed of SPRRR repeats and are effective against both Gram-positive and Gram-negative bacteria, as well as fungi. We found different bactericidal mechanisms of the ARD peptides, which involved LPS binding, DNA binding and membrane permeabilization in various tested bacteria, such as P. aeruginosa, K. pneumoniae, E. coli and S. aureus. We also found that this ARD peptide was effective for colistin-resistant A. baumannii. The peptides exhibited no hemolysis activity to human red blood cells and no cytotoxicity to human hepatoma cells and kidney cells. Furthermore, the ARD peptide was shown to be safe and protective in the animal model. Recently, intestinal flora was found to influence the development of immunity. We discussed here the potential involvement of the antimicrobial activity of HBc ARD in the establishment of HBV chronic infection in the newborns. We proposed here that the HBc ARD peptides could serve as an alternative to the conventional antibiotics in clinical medicine.

A novel approach for normalizing the photoreflectance spectrum by using polymer-dispersed liquid crystal

This study developed a novel type of normalization procedure for modulation reflectance spectroscopy experiments to obtain the relative change in the reflectance spectrum, ΔR/R. This technique uses a polymer-dispersed liquid crystal to ensure that the dc component of the signal from the detector remained constant by varying the intensity of the light striking the sample. This method is particularly useful for photoreflectance measurement, which may encounter background problems because of scattered pump light and/or photoluminescence. It does not require a change in the gain of the detector or the use of a variable neutral density filter mounted on a servo-motor.

Outer membrane lipoprotein Lpp is Gram-negative bacterial cell surface receptor for cationic antimicrobial peptides

Antimicrobial peptides/proteins (AMPs) are important components of the host innate defense mechanisms. Here we demonstrate that the outer membrane lipoprotein, Lpp, of Enterobacteriaceae interacts with and promotes susceptibility to the bactericidal activities of AMPs. The oligomeric Lpp was specifically recognized by several cationic α-helical AMPs, including SMAP-29, CAP-18, and LL-37; AMP-mediated bactericidal activities were blocked by anti-Lpp antibody blocking. Blebbing of the outer membrane and increase in membrane permeability occurred in association with the coordinate internalization of Lpp and AMP. Interestingly, the specific binding of AMP to Lpp was resistant to divalent cations and salts, which were able to inhibit the bactericidal activities of some AMPs. Furthermore, using His-tagged Lpp as a ligand, we retrieved several characterized AMPs, including SMAP-29 and hRNase 7, from a peptide library containing crude mammalian cell lysates. Overall, this study explores a new mechanism and target of antimicrobial activity and provides a novel method for screening of antimicrobials for use against drug-resistant bacteria.

NMR and biophysical elucidation of structural effects on extra N-terminal methionine residue of recombinant amphibian RNases from Rana catesbeiana

The stability, structures and steric hindrances of recombinant RNases 2 and 4 expressed in bacteria were studied by circular dichroism (CD) and NMR techniques, and the results were compared with those of their authentic RNases extracted from oocytes of Rana catesbeiana. Although the overall structures of the recombinant and authentic proteins are almost identical, the extra N-terminal Met residue of the recombinant protein remarkably affects catalytic activity and stability. NMR chemical shift comparison of recombinant RNases and the authentic proteins indicated that the structural differences are mainly confined to the N-terminal helical and S2 anti-parallel beta-sheet regions. Significant shift changes for the residues located on the S2 region indicate that the major influences on the structure around the N terminus is due to the loss of the hydrogen bond between Pyr(1) and Val(95(96)) in recombinant RNases 2 and 4. We concluded the apparent steric hindrances of the extra Met to the binding pocket. As well, the affected conformational changes of active residues are attributed to the reduced activities of recombinant RNases. The structural integrity exerted by the N-terminal Pyr(1) residue may be crucial for amphibian RNases and the greatest structural differences occur on the network of the Pyr(1) residue and S2 beta-sheet region.

Outer membrane protein I of Pseudomonas aeruginosa is a target of cationic antimicrobial peptide/protein

Cationic antimicrobial peptides/proteins (AMPs) are important components of the host innate defense mechanisms against invading microorganisms. Here we demonstrate that OprI (outer membrane protein I) of Pseudomonas aeruginosa is responsible for its susceptibility to human ribonuclease 7 (hRNase 7) and alpha-helical cationic AMPs, instead of surface lipopolysaccharide, which is the initial binding site of cationic AMPs. The antimicrobial activities of hRNase 7 and alpha-helical cationic AMPs against P. aeruginosa were inhibited by the addition of exogenous OprI or anti-OprI antibody. On modification and internalization of OprI by hRNase 7 into cytosol, the bacterial membrane became permeable to metabolites. The lipoprotein was predicted to consist of an extended loop at the N terminus for hRNase 7/lipopolysaccharide binding, a trimeric alpha-helix, and a lysine residue at the C terminus for cell wall anchoring. Our findings highlight a novel mechanism of antimicrobial activity and document a previously unexplored target of alpha-helical cationic AMPs, which may be used for screening drugs to treat antibiotic-resistant bacterial infection.

Granulysin is a key mediator for disseminated keratinocyte death in Stevens-Johnson syndrome and toxic epidermal necrolysis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening adverse drug reactions characterized by massive epidermal necrosis, in which the specific danger signals involved remain unclear. Here we show that blister cells from skin lesions of SJS-TEN primarily consist of cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells, and both blister fluids and cells were cytotoxic. Gene expression profiling identified granulysin as the most highly expressed cytotoxic molecule, confirmed by quantitative PCR and immunohistochemistry. Granulysin concentrations in the blister fluids were two to four orders of magnitude higher than perforin, granzyme B or soluble Fas ligand concentrations, and depleting granulysin reduced the cytotoxicity. Granulysin in the blister fluids was a 15-kDa secretory form, and injection of it into mouse skin resulted in features mimicking SJS-TEN. Our findings demonstrate that secretory granulysin is a key molecule responsible for the disseminated keratinocyte death in SJS-TEN and highlight a mechanism for CTL- or NK cell--mediated cytotoxicity that does not require direct cellular contact.

The flexible and clustered lysine residues of human ribonuclease 7 are critical for membrane permeability and antimicrobial activity

The ubiquitous ribonucleases (RNases) play important roles in RNA metabolism, angiogenesis, neurotoxicity, and antitumor or antimicrobial activity. Only the antimicrobial RNases possess high positively charged residues, although their mechanisms of action remain unclear. Here, we report on the role of cationic residues of human RNase7 (hRNase7) in its antimicrobial activity. It exerted antimicrobial activity against bacteria and yeast, even at 4 degrees C. The bacterial membrane became permeable to the DNA-binding dye SYTOX(R) Green in only a few minutes after bactericidal RNase treatment. NMR studies showed that the 22 positively charged residues (Lys(18) and Arg(4)) are distributed into three clusters on the surface of hRNase7. The first cluster, K(1),K(3),K(111),K(112), was located at the flexible coil near the N terminus, whereas the other two, K(32),K(35) and K(96),R(97),K(100), were located on rigid secondary structures. Mutagenesis studies showed that the flexible cluster K(1),K(3),K(111),K(112), rather than the catalytic residues His(15), Lys(38), and His(123) or other clusters such as K(32),K(35) and K(96),R(97),K(100), is critical for the bactericidal activity. We suggest that the hRNase7 binds to bacterial membrane and renders the membrane permeable through the flexible and clustered Lys residues K(1),K(3),K(111),K(112). The conformation of hRNase7 can be adapted for pore formation or disruption of bacterial membrane even at 4 degrees C.

Roles of N-terminal pyroglutamate in maintaining structural integrity and pKa values of catalytic histidine residues in bullfrog ribonuclease 3

Many proteins and bioactive peptides contain an N-terminal pyroglutamate residue (Pyr1). This residue reduces the susceptibility of the protein to aminopeptidases and often has important functional roles. The antitumor ribonuclease RC-RNase 3 (RNase 3) from oocytes of Rana catesbeiana (bullfrog) is one such protein. We have produced recombinant RNase 3 containing the N-terminal Pyr1 (pRNase 3) and found it to be indistinguishable from the native RNase 3 by mass spectrometry and a variety of other biochemical and immunological criteria. We demonstrated by NMR analysis that the Pyr1 of pRNase 3 forms hydrogen bonds with Lys9 and Ile96 and stabilizes the N-terminal alpha-helix in a rigid conformation. In contrast, the N-terminal alpha-helix becomes flexible and the pKa values of the catalytic residues His10 and His97 altered when Pyr1 formation is blocked by an extra methionine at the N terminus in the recombinant mqRNase 3. Thus, our results provide a mechanistic explanation on the essential role of Pyr1 in maintaining the structural integrity, especially at the N-terminal alpha-helix, and in providing the proper environment for the ionization of His10 and His97 residues for catalysis and cytotoxicity against HeLa cells.

Removal of N-terminal methionine from recombinant proteins by engineered E. coli methionine aminopeptidase

The removal of N-terminal translation initiator Met by methionine aminopeptidase (MetAP) is often crucial for the function and stability of proteins. On the basis of crystal structure and sequence alignment of MetAPs, we have engineered Escherichia coli MetAP by the mutation of three residues, Y168G, M206T, Q233G, in the substrate-binding pocket. Our engineered MetAPs are able to remove the Met from bulky or acidic penultimate residues, such as Met, His, Asp, Asn, Glu, Gln, Leu, Ile, Tyr, and Trp, as well as from small residues. The penultimate residue, the second residue after Met, was further removed if the antepenultimate residue, the third residue after Met, was small. By the coexpression of engineered MetAP in E. coli through the same or a separate vector, we have successfully produced recombinant proteins possessing an innate N terminus, such as onconase, an antitumor ribonuclease from the frog Rana pipiens. The N-terminal pyroglutamate of recombinant onconase is critical for its structural integrity, catalytic activity, and cyto-toxicity. On the basis of N-terminal sequence information in the protein database, 85%-90% of recombinant proteins should be produced in authentic form by our engineered MetAPs.

The structural integrity exerted by N-terminal pyroglutamate is crucial for the cytotoxicity of frog ribonuclease from Rana pipiens

Onconase, a cytotoxic ribonuclease from Rana pipiens, possesses pyroglutamate (Pyr) at the N-terminus and has a substrate preference for uridine-guanine (UG). To identify residues responsible for onconase's cytotoxicity, we cloned the rpr gene from genomic DNA and expressed it in Escherichia coli BL21(DE3). The recombinant onconase with Met at the N-terminus had reduced thermostability, catalytic activity and antigenicity. Therefore, we developed two methods to produce onconase without Met. One relied on the endogeneous E.coli methionine aminopeptidase and the other relied on the cleavage of a pelB signal peptide. The Pyr1 substitutional variants maintained similar secondary structures to wild-type onconase, but with less thermostability and specific catalytic activity for the innate substrate UG. However, the non-specific catalytic activity for total RNAs varied depending on the relaxation of base specificity. Pyr1 promoted the structural integrity by forming a hydrogen bond network through Lys9 in alpha1 and Val96 in beta6, and participated in catalytic activity by hydrogen bonds to Lys9 and P(1) catalytic phosphate. Residues Thr35 and Asp67 determined B(1) base specificity, and Glu91 determined B(2) base specificity. The cytotoxicity of onconase is largely determined by structural integrity and specific catalytic activity for UG through Pyr1, rather than non-specific activity for total RNAs.

Residues involved in the catalysis, base specificity, and cytotoxicity of ribonuclease from Rana catesbeiana based upon mutagenesis and X-ray crystallography

The Rana catesbeiana (bullfrog) ribonucleases, which belong to the RNase A superfamily, exert cytotoxicity toward tumor cells. RC-RNase, the most active among frog ribonucleases, has a unique base preference for pyrimidine-guanine rather than pyrimidine-adenine in RNase A. Residues of RC-RNase involved in base specificity and catalytic activity were determined by site-directed mutagenesis, k(cat)/K(m) analysis toward dinucleotides, and cleavage site analysis of RNA substrate. The results show that Pyr-1 (N-terminal pyroglutamate), Lys-9, and Asn-38 along with His-10, Lys-35, and His-103 are involved in catalytic activity, whereas Pyr-1, Thr-39, Thr-70, Lys-95, and Glu-97 are involved in base specificity. The cytotoxicity of RC-RNase is correlated, but not proportional to, its catalytic activity. The crystal structure of the RC-RNase.d(ACGA) complex was determined at 1.80 A resolution. Residues Lys-9, His-10, Lys-35, and His-103 interacted directly with catalytic phosphate at the P(1) site, and Lys-9 was stabilized by hydrogen bonds contributed by Pyr-1, Tyr-28, and Asn-38. Thr-70 acts as a hydrogen bond donor for cytosine through Thr-39 and determines B(1) base specificity. Interestingly, Pyr-1 along with Lys-95 and Glu-97 form four hydrogen bonds with guanine at B(2) site and determine B(2) base specificity.

Solution structure of the cytotoxic RNase 4 from oocytes of bullfrog Rana catesbeiana

Cytotoxic ribonucleases with antitumor activity are mainly found in the oocytes and early embryos of frogs. Native RC-RNase 4 (RNase 4), consisting of 106 residues linked with four disulfide bridges, is a cytotoxic ribonuclease isolated from oocytes of bullfrog Rana catesbeiana. RNase 4 belongs to the bovine pancreatic ribonuclease (RNase A) superfamily. Recombinant RC-RNase 4 (rRNase 4), which contains an additional Met residue and glutamine instead of pyroglutamate at the N terminus, was found to possess less catalytic and cytotoxic activities than RNase 4. Equilibrium thermal and guanidine-HCl denaturation CD measurements revealed that RNase 4 is more thermally and chemically stable than rRNase 4. However, CD and NMR data showed that there is no gross conformational change between native and recombinant RNase 4. The NMR solution structure of rRNase 4 was determined to comprise three alpha-helices and two sets of antiparallel beta-sheets. Superimposition of each structure with the mean structure yielded an average root mean square deviation (RMSD) of 0.72(+/-0.14)A for the backbone atoms, and 1.42(+/-0.19)A for the heavy atoms in residues 3-105. A comparison of the 3D structure of rRNase 4 with the structurally and functionally related cytotoxic ribonuclease, onconase (ONC), showed that the two H-bonds in the N-terminal pyroglutamate of ONC were not present at the corresponding glutamine residue of rRNase 4. We suggest that the loss of these two H-bonds is one of the key factors responsible for the reductions of the conformational stability, catalytic and cytotoxic activities in rRNase 4. Furthermore, the differences of side-chain conformations of subsite residues among RNase A, ONC and rRNase 4 are related to their distinct catalytic activities and base preferences.

Regulation of ribonuclease expression by estradiol in Rana catesbeiana (Bullfrog)

Multiple ribonucleases are widely found in living organisms, but the function and regulation of individual ribonucleases are still not clear. In the present study, we found that one oocytic ribonuclease, RC-RNase, is developmentally expressed in the liver and stored in the oocyte of the bullfrog, while another ribonuclease, RC-RNase L1, is constitutively expressed and retained in the liver at all stages. In females, the expression of RC-RNase increased with the degree of maturity and the concentration of plasma estradiol during oogenesis. In males, the RC-RNase gene was activated in the liver and the newly synthesized protein was secreted into plasma if estradiol was administered. To investigate the mechanism of estrogen-mediated activation of ribonuclease expression, we cloned the RC-RNase promoter and analyzed the putative transcription factor binding sites, e.g. TATA box, ERE, AP1 and CAAT box. Using luciferase as a reporter gene, we found that an estrogen response element in the promoter of RC-RNase was essential for both basic transcription and estradiol-mediated gene activation in estrogen receptor-positive MCF7 cells. These results support the hypothesis that RC-RNase is synthesized in the liver upon stimulation by estradiol during oogenesis, then secreted into the bloodstream and stored in oocytes for embryonic development.

Crystallization and preliminary X-ray diffraction analysis of cytotoxic ribonucleases from bullfrog Rana catesbeiana

RC-RNases are ribonucleases from Rana catesbeiana oocytes with pyrimidine-guanine sequence specificity. They also possess cell cytotoxicity and lectin activity. Protein crystals of three RC-RNase isozymes, RC-RNase 3, RC-RNase 4 and RC-RNase 6, were grown in various crystal systems under different conditions. Crystals of RC-RNase3 belong to the orthorhombic C222(1) space group, with unit-cell parameters a = 66.66, b = 97.38, c = 85.74 A. Crystals of RC-RNase 4 belong to the trigonal space group P3(1) or P3(2), with unit-cell parameters a = b = 32.22, c = 92.12 A. Crystals of RC-RNase 6 complexed with cytidylyl 2'-5' guanosine belong to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell parameters a = b = 61.80, c = 65.96 A.

Rapid diversification of RNase A superfamily ribonucleases from the bullfrog, Rana catesbeiana

We present sequences of five novel RNase A superfamily ribonuclease genes of the bullfrog, Rana catesbeiana. All five genes encode ribonucleases that are similar to Onconase, a cytotoxic ribonuclease isolated from oocytes of R. pipiens. With amino acid sequence data from 14 ribonucleases from three Rana species (R. catesbeiana, R. japonica, and R. pipiens), we have constructed bootstrap-supported phylogenetic trees that reorganize these ribonucleases into five distinct lineages--the pancreatic ribonucleases (RNases 1), the eosinophil-associated ribonucleases (RNases 2, 3, and 6), the ribonucleases 4, the angiogenins (RNases 5) and the Rana ribonucleases--with the Rana ribonucleases no more closely related to the angiogenins than they are to any of the other ribonuclease lineages shown. Further phylogenetic analysis suggests the division of the Rana ribonucleases into two subclusters (A and B), with positive (Darwinian) selection (dN/dS > 1.0) and an elevated rate of radical nonsynonymous substitution (dR) contributing to the rapid diversification of ribonucleases within each cluster. This pattern of evolution-rapid diversification via positive selection among sequences of a multigene cluster-bears striking resemblance to what we have described for the eosinophil-associated ribonuclease genes of the rodent Mus musculus, a finding that may have implications with respect the physiologic function of this unique family of proteins.

Purification and cloning of cytotoxic ribonucleases from Rana catesbeiana (bullfrog)

Ribonucleases with antitumor activity are mainly found in the oocytes and embryos of frogs, but the role of these ribonucleases in frog development is not clear. Moreover, most frog ribonuclease genes have not been cloned and characterized. In the present study, a group of ribonucleases were isolated from Rana catesbeiana (bullfrog). These ribonucleases in mature oocytes, namely RC-RNase, RC-RNase 2, RC-RNase 3, RC-RNase 4, RC-RNase 5 and RC-RNase 6, as well as liver-specific ribonuclease RC-RNase L1, were purified by column chromatographs and detected by zymogram assay and western blotting. Characterization of these purified ribonucleases revealed that they were highly conserved in amino acid sequence and had a pyroglutamate residue at their N-termini, but possessed different specific activities, base specificities and optimal pH values for their activities. These ribonucleases were cytotoxic to cervical carcinoma HeLa cells, but their cytotoxicities were not closely correlated to their enzymatic specific activities. Some other amino acid residues in addition to their catalytic residues were implicated to be involved in the cytotoxicity of the frog ribonucleases to tumor cells. Because the coding regions lack introns, the ribonuclease genes were cloned by PCR using genomic DNA as template. Their DNA sequences and amino acid sequences are homologous to those of mammalian ribonuclease superfamily, approximately 50 and approximately 25%, respectively.

The Rana catesbeiana rcr gene encoding a cytotoxic ribonuclease. Tissue distribution, cloning, purification, cytotoxicity, and active residues for RNase activity

Rana catesbeiana ribonuclease (RC-RNase) is a pyrimidine-guanine sequence-specific ribonuclease found in R. catesbeiana (bullfrog) oocytes. It possesses both ribonuclease activity and cytotoxicity against tumor cells. We report here for the first time the cloning of RC-RNase cDNA from liver rather than from oocytes where RC-RNase is stored. An internal fragment of cDNA was obtained by reverse transcription-PCR using deduced oligonucleotides as primers. Full-length cDNA was obtained by 5'- and 3'-RACE technique. The cDNA clone, named rcr gene, contained a 5'-untranslated region, a putative signal peptide (22 amino acids), a mature protein (111 amino acids), a 3'-untranslated region, and a polyadenylation site. The cDNA which encoded the mature protein was fused upstream with a modified pelB signal peptide DNA and inserted into pET11d for expression in Escherichia coli strain BL21(DE3). The secretory RC-RNase in the culture medium was enzymatically active and was purified to homogeneity. The recombinant RC-RNase had the same amino acid sequence, specific activity, substrate specificity, antigenicity, and cytotoxicity as that of native RC-RNase from frog oocytes. Amino acid residues His-10, Lys-35, and His-103 are involved in RC-RNase catalytic activity. Ribonucleolytic activity was involved in and may be essential for RC-RNase cytotoxicity. DNA sequence analysis showed that RC-RNase had approximately 45% identity to that of RNase superfamily genes. This indicates that RC-RNase is a distinct ribonuclease gene in the RNase superfamily.

The secondary structure of a pyrimidine-guanine sequence-specific ribonuclease possessing cytotoxic activity from the oocytes of Rana catesbeiana

RC-RNase is a pyrimidine-guanine sequence-specific ribonuclease and a sialic-acid-binding lectin purified from Rana catesbeiana (bullfrog) oocytes. This 111-amino acid protein exhibits cytotoxicity toward several tumor cell lines. In this paper we report the assignments of proton NMR resonances and the identification of the secondary structure deduced from NOE constraints, chemical shift index, 3JNH alpha and amide proton exchange rates. The protein was directly isolated from bullfrog oocytes; we were able to assign all but five of the amino acid backbone protons of the unlabeled protein by analyzing a large set of two-dimensional proton NMR spectra obtained at several temperatures and pH conditions. Our results indicate that the structure of RC-RNase is dominated by the presence of two triple-stranded antiparallel beta-sheets and three alpha-helices, similar to those of the pyrimidine family ribonucleases. Two sets of resonances were observed for 11 amide protons and 8 alpha-protons located in the loop-1 region, an alpha 2 helix, and three beta-strands, (beta 1, beta 3 and beta 4), suggesting the presence of nonlocalized multiple conformations for RC-RNase.

Large-scale preparation of a ribonuclease from Rana catesbeiana (bullfrog) oocytes and characterization of its specific cytotoxic activity against tumor cells

Rana catesbeiana ribonuclease (RC-RNase) is a pyrimidine-guanine sequence-specific ribonuclease found only in R. catesbeiana (bullfrog) oocytes, but not in other organs. The protein is localized in the yolk granules of oocytes but not in other organelles, as detected by immunohistochemistry. More than 99% of RC-RNase was found in the yolk granule pellet when a mild separation method was employed under physiological conditions. The ribonuclease was purified by precipitation of yolk granules, extraction of RC-RNase with 0.09 M NaCl, selective removal of impurities by Hepes buffer, and chromatographies on phosphocellulose and carboxymethyl cellulose columns. Three milligrams of RC-RNase was purified from a 1-g pellet of yolk granules prepared from 2 g of ovary tissue. Therefore, 150 milligrams of RC-RNase could be obtained from a mature female bullfrog (600 g in weight) which had 100 g of ovary tissue. The properties of RC-RNase isolated from yolk granules tested so far are identical to those of RC-RNase isolated from the cytosolic fraction and similar to those of a sialic acid-binding lectin from bullfrog oocytes. To investigate the possible role of RC-RNase in the regulation of cell growth and differentiation during embryogenesis, its cytotoxic activity against various cell lines was examined. The degradation of ribosomal RNA was found in RC-RNase-treated HeLa cells. However, both events were not found in RNase A-treated HeLa cells. Therefore, RC-RNase is proposed to have both ribonucleolytic and cytotoxic activity and a specific receptor on the tumor cell surface is suspected to be involved in the recognition and binding, and possibly entry of RC-RNase.

Immunocytochemical localization of ribonuclease in yolk granules of adult Rana catesbeiana oocytes

To determine the localization of the pyrimidine-guanine sequence-specific ribonuclease in Rana catesbeiana (bullfrog) oocytes, the RNase was first isolated and used to prepare a specific rabbit antiserum. Only one protein of similar molecular size to the RNase was immunoprecipitated from ovary homogenate by the antiserum, but two bands were observed by Western blotting analysis. These two proteins were shown by further purification of antibody and Western blotting analysis to have similar antigenicity. Immunoprecipitation and Western blotting of tissue homogenates showed that the RNase was found predominantly in the ovary, but not in other tissues. The specific localization of the RNase was determined by immuno-electron microscopy of oocyte sections incubated with the specific antiserum; the yolk granules, but not other organelles, were found to contain the RNase. Most of the RNase was evenly distributed in the lateral amorphous area of the yolk granule but not in the central yolk crystal area which contains stored vitellogenin proteins. Our results indicate that the RNase is compartmentalized in the yolk granules of oocytes, which might prevent damage to cellular RNAs.

Determination of base specificity of multiple ribonucleases from crude samples

Ribonucleases are widely found on the tissues of living organisms, but the functions of individual ribonucleases are not clear. To facilitate characterization of individual ribonucleases, I have developed a rapid method to separate and identify each ribonuclease from a crude sample by gel electrophoresis instead of by time-consuming purification steps. The ribonucleases in a crude sample are first separated by RNA-cast SDS-polyacrylamide gel electrophoresis and then eluted from the gel after ethidium bromide staining. To determine the base specificity of each ribonuclease, a 5' labelled oligonucleotide with known sequence is added to the enzyme eluate and the digested products are analyzed by denaturing gel electrophoresis. The base specificity of bovine pancreatic ribonuclease (RNase A), bullfrog oocyte-specific ribonuclease (RC-RNase), human serum ribonucleases and sweet potato leaf ribonucleases were determined by this method. Other properties of individual ribonucleases, e.g. substrate preference, may also be determined from crude samples by this method without further purification steps.

Yolk granules are the major compartment for bullfrog (Rana catesbeiana) oocyte-specific ribonuclease

Rana catesbeiana ribonuclease (RC-RNase) is a pyrimidine guanine sequence-specific ribonuclease found only in R. catesbeiana (bullfrog) oocytes, not in other organs. An immunohistochemical assay showed that RC-RNase was present in the regular yolk granules, but not in forming yolk granules, yolk platelets, pigment granules, mitochondria clouds or the nucleus. The RC-RNase was restricted to the lateral amorphous area of the yolk granules, and was absent from the central area that has a vitellogenin crystal lattice. The RC-RNase was extracted from yolk granules by 0.5 M NaCl and purified by dialysis and affinity chromatography. Most of the RC-RNase (94%) was found in the yolk granules, the rest RC-RNase (6%) was found in the cytosol in the form of free RNase and latent RNase. The RC-RNase extracted from yolk granules was further analyzed by immunoprecipitation and RNase activity assay on an SDS/polyacrylamide gel. Our results suggest that the RC-RNase activity is regulated by both compartmentation and inhibitor binding.

A pyrimidine-guanine sequence-specific ribonuclease from Rana catesbeiana (bullfrog) oocytes

A pyrimidine-guanine sequence-specific ribonuclease (RC-RNase) was purified from Rana catesbeiana (bullfrog) oocytes by sequential phosphocellulose, Sephadex G75, heparin Sepharose CL 6B and CM-Sepharose CL 6B column chromatography. The purified enzyme with molecular weight of 13,000 daltons gave a single band on SDS-polyacrylamide gel. One CNBr-cleaved fragment has a sequence of NVLSTTRFQLNT/TRTSITPR, which is identical to residues 59-79 of a sialic acid binding lectin from R. catesbeiana eggs, and is 71% homologous to residues 60-80 of an RNase from R. catesbeaina liver. The RC-RNase preferentially cleaved RNA at pyrimidine residues with a 3' flanking guanine under various conditions. The sequence specificity of RC-RNase was further confirmed with dinucleotide as substrates, which were analyzed by thin layer chromatography after enzyme digestion. The values of kcat/km for pCpG, pUpG and pUpU were 2.66 x 10(7) M-1s-1, 2.50 x 10(7) M-1s-1 and 2.44 x 10(6) M-1s-1 respectively, however, those for other phosphorylated dinucleotides were less than 2% of pCpG and pUpG. As compared to single strand RNA, double strand RNA was relatively resistant to RC-RNase. Besides poly (A) and poly (G), most of synthetic homo- and heteropolynucleotides were also susceptible to RC-RNase. The RC-RNase was stable in the acidic (pH 2) and alkaline (pH 12) condition, but could be inactivated by heating to 80 degrees C for 15 min. No divalent cation was required for its activity. Furthermore, the enzyme activity could be enhanced by 2 M urea, and inhibited to 50% by 0.12 M NaCl or 0.02% SDS.

Zinc release from Xenopus transcription factor IIIA induced by chemical modifications

Xenopus transcription factor IIIA (TFIIIA) contains two tightly bound intrinsic Zn2+ ions that are released through treatment with either p-(hydroxymercuri)benzenesulfonate (PMPS) or diethyl pyrocarbonate (DEP) as monitored by the metallochromic indicator 4-(2-pyridylazo)resorcinol (PAR). The inactivation of TFIIIA by DEP as detected by an in vitro 5S RNA gene transcription assay was correlated with the extent of modification of histidine residues and Zn2+ release. Following reaction with PMPS, the 7S particle was dissociated into free TFIIIA and 5S RNA. This dissociation could be correlated with the extent of modification of cysteine residues as well as the Zn2+ release. The dissociation of the 7S particle was reversed by the addition of excess thiol reagent. However, the reversibility could be inhibited by EDTA, suggesting that Zn2+ was required for the binding of TFIIIA to 5S RNA. In the presence of PMPS- or DEP-modified TFIIIA or Zn2+-depleted TFIIIA, the fluorescence emission maximum of the hydrophobic probe, 8-anilinonaphthalenesulfonate, was blue-shifted by 30 nm, while only less than a 10-nm blue shift was observed in the presence of either the 7S particle or TFIIIA. These results indicate that the two Zn2+ ions in TFIIIA are coordinated with the cysteine and histidine residues and are required for maintenance of the proper conformation of TFIIIA.

An N-terminally fused Xenopus transcription factor IIIA synthesized in Escherichia coli is biologically active

A 1.5-kilobase DNA fragment containing the Xenopus transcription factor IIIA (TFIIIA) gene was inserted into the prokaryotic expression vector pIN-III(A) containing the lpp/lac promoter. The recombinant DNA was introduced into Escherichia coli K-12 strain SB221. The expression TFIIIA gene was induced by isopropyl-beta-D-thiogalactopyranoside, which resulted in the synthesis of a recombinant TFIIIA with an extra 17 amino acids fused to its N terminus as predicted from the nucleotide sequence. The engineered gene product, purified to at least 90% homogeneity, retained its binding affinity to the intragenic control region of the 5 S RNA gene, as well as its activity to stimulate 5 S RNA gene transcription in vitro.

Purification of Xenopus transcription factor IIIA and 5 S RNA from 7 S ribonucleoprotein particle by ammonium sulfate precipitation

A simple and efficient method for purifying Xenopus transcription factor IIIA from the 7 S particle has been developed by taking advantage of the differential solubilities of the protein factor and 5 S RNA in ammonium sulfate solution. Conditions under which ammonium sulfate dissociates the 7 S particle and selectively precipitates factor IIIA while the 5 S RNA moiety remains in the supernatant were found. The method simultaneously purifies, in a nondestructive manner, both factor IIIA and 5 S RNA in high yield. Purification proceeds through several ammonium sulfate precipitations of the 7 S particle. Factor IIIA obtained by this method contains no detectable RNA and is highly active as judged by DNase I footprinting and in vitro transcription of the 5 S RNA gene, as well as reconstitution with 5 S RNA to form the 7 S particle. The molar extinction coefficients of factor IIIA at 205 and 280 nm were determined from the ultraviolet absorption spectra measured with the purified protein.

Regulation of transcription of the Xp10 genome in bacteriophage-infected Xanthomonas campestris pv. oryzae

Results of in vivo studies showed that the transcription of the Xp10 genome in Xp10-infected cells shifted from rifampin sensitivity to rifampin resistance. Results of in vitro studies showed that a rapid reduction of rifampin-sensitive RNA polymerase activity coincided with a rapid increase of rifampin-resistant RNA polymerase activity in cell extracts with time after infection. Host and Xp10-encoded RNA polymerases were purified, and the transcripts from these two enzymes were hybridized to the restriction fragments of Xp10 DNA. The RNA probe generated by host RNA polymerase hybridized strongly to the leftmost 25% of Xp10 DNA and weakly to the rightmost 75% of Xp10 DNA. The RNA probe generated by Xp10 RNA polymerase hybridized strongly to the rightmost 75% of Xp10 DNA and weakly to the leftmost 25% of Xp10 DNA. Studies with 32P-labeled RNA isolated at various intervals after infection did not reveal any evidence for early versus late differences in transcription.

Loss of sigma-factor of RNA polymerase of Xanthomonas campestris pv. oryzae during phage Xp10 infection

Ten min after infection of Xanthomonas campestris pv. oryzae by phage Xp10, a sharp decrease in the activity of the host RNA polymerase was observed. Host RNA polymerase from phage-infected and uninfected cells was purified, and their properties were compared. The enzyme from uninfected cells contained four polypeptides with Mr = 155,000, 155,000, 93,000, and 37,000, respectively, and assembled with a stoichiometry of alpha 2 beta beta' sigma. The enzyme from infected cells lacked the sigma-subunit. The enzyme from uninfected cells utilized Xp10 DNA and poly[d(A-T)] as templates, the enzyme from phage-infected cells failed to transcribe Xp10 DNA, but retained the ability to transcribe poly(A-T). The regions of the Xp10 genome transcribed by the two enzymes were also investigated. The enzyme from uninfected cells transcribed the leftmost 25-30% of the Xp10 genome. The enzyme from phage-infected cells also transcribed the same region, but the enzyme activity was very low. Other properties such as (a) the response to RNA polymerase inhibitors, (b) the effect of N-ethylmaleimide, (c) the requirement of Mg2+ and Mn2+, and (d) the optimum temperature and pH of the two enzymes were very similar.

Characterization of phage-Xp10-coded RNA polymerase

A bacteriophage-coded RNA polymerase was isolated from bacteriophage-Xp10-infected Xanthomonas campestris pv. oryzae. The enzyme was purified to homogeneity through precipitation by poly(ethylene glycol) and chromatography on DEAE-cellulose, heparin--Sepharose 4B and blue-dextran--Sepharose 4B. It is composed of a single polypeptide of Mr96,000. The enzyme preferred denatured Xp10 DNA, calf thymus DNA, host bacterium DNA and poly[d(A-T)] as templates. The optimal concentration of MgCl2 is 16 mM. The optimal temperature and pH are 37 degrees C and 8.0, respectively. The Km of ATP is 26 microM. DNA, MgCl2 and four ribonucleotides were required for enzyme activity. If ATP alone was present, half of the Xp10 RNA polymerase activity was retained. The enzyme activity was inhibited by KCl, spermidine, actinomycin D, heparin, blue dextran and ethidium bromide; it was resistant to rifampicin and streptovaricin. N-Ethylmaleimide did not affect the enzyme activity. The transcription site and product of Xp10 RNA polymerase upon Xp10 DNA were analyzed by DNA/RNA hybridization and polyacrylamide-agarose composite gel electrophoresis. The enzyme could specifically transcribe the late region of Xp10 genome and produce two RNA bands.