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Biomedical subjects

H Guan

Publications and source records attributed to H Guan.

At least 19 recordsLinked to original sources
PubMed2003

A novel polygalacturonic acid bioflocculant REA-11 produced by Corynebacterium glutamicum: a proposed biosynthetic pathway and experimental confirmation.

Corynebacterium glutamicum CCTCC M201005 produces a novel polygalacturonic acid bioflocculant, REA-11, consisting of galacturonic acid as the main structural unit. A biosynthetic pathway of REA-11 in C. glutamicum CCTCC M201005 was proposed. Evidence for the biosynthetic pathway was provided by: (1) analyzing the response upon addition of UDP-glucose to the culture medium; (2) detecting the presence of several key intermediates in the pathway; and (3) correlating the activities of several key enzymes involved in the pathway with the yields of polygalacturonic acid. The production of polygalacturonic acid was improved by 24%, while the activities of UDP-galactose epimerase and UDP-galactose dehydrogenase were improved by 200% and 50%, respectively, upon addition of 100 microM UDP-glucose. In addition, the key intermediates in the proposed biosynthetic pathway, such as UDP-glucose, UDP-galactose, and UDP-glucuronic acid, were detected in cell-free extracts. Furthermore, the activities of UDP-glucose pyrophosphorylase (R2=0.97), UDP-galactose epimerase (R2=0.75) and UDP-galactose dehydrogenase (R2=0.89) were well correlated with the yields of polygalacturonic acid when different sugars were used as sole carbon sources. Therefore, the biosynthetic pathway of REA-11 in C. glutamicum CCTCC M201005 starts from phosphate-1-glucose, which was then converted to UDP-glucose by UDP-pyrophosphorylase. Predominantly, the UDP-glucose was converted to UDP-galactose by UDP-galactose epimerase; the latter was further converted to UDP-galacturonic acid by UDP-galactose dehydrogenase, which was presumably polymerized to polygalacturonic acid bioflocculant REA-11 by an unknown glucosyltransferase and a polymerase.

Corynebacterium↗
PubMed2003

Transgenic twin lambs cloned by granulosa cells.

The development potential of transgenic adult cells after nuclear transfer (NT) was evaluated. Primary ovine granulosa cells (GC(S)) from a slaughter ovary were transfected with pEGFP-N1 plasmid DNA. Three G418-resistance cell lines (A2, B2 and B4) were used as donor cells in NT. A total of 162 NT blastocysts were then frozen with ethylene glycol solution and stored for five months before transplanted into recipients. Twenty-nine frozen thawed NT blastocysts were transferred into 15 synchronized recipients. Twin lambs (6.9%) derived from B2 line were delivered by cesarean section on day 143 but died after birth. A tumor consisting of lung tissues was found on the surface of left lung of the 4-kg lamb and histological analysis indicated that it resembles a hamartoma. DNA analysis confirmed that two lambs were genetically identical to B2 donor cells. Gene insertion and expression have been detected in fibroblasts cells derived from muscle tissues of the lambs. This study indicates that granulosa cell is a suitable cell type for producing transgenic animals by nuclear transfer. Offspring were produced after long-term storage of NT blastocysts.

Animals↗
PubMed2001

The Sushi domain of soluble IL-15 receptor alpha is essential for binding IL-15 and inhibiting inflammatory and allogenic responses in vitro and in vivo.

IL-15 is a pleiotropic cytokine that plays important roles in both innate and adaptive immunity. It is associated with a range of immunopathology, including rheumatoid arthritis and allograft rejection. IL-15 functions through the trimeric IL-15R complex, which consists of a high affinity binding alpha-chain and the common IL-2R beta- and gamma-chains. Characterization of IL-15/IL-15R interactions may facilitate the development of improved IL-15 antagonists for therapeutic interventions. We previously constructed soluble murine IL-15Ralpha (sIL-15Ralpha) by deleting the cytoplasmic and transmembrane domains. To localize the functional domain of IL-15Ralpha, we have now constructed various truncated versions of sIL-15Ralpha. The shortest region retaining IL-15 binding activity is a 65-aa sequence spanning the Sushi domain of IL-15Ralpha. Sushi domains, common motifs in protein-protein interactions, contain four cysteines forming two disulfide bonds in a 1-3 and 2-4 pattern. Amino acid substitution of the first or fourth cysteine in sIL-15Ralpha completely abolished its IL-15 binding activity. This also abrogated the ability of sIL-15Ralpha to neutralize IL-15-induced proinflammatory cytokine production and anti-apoptotic response in vitro. Furthermore, the mutant sIL-15Ralpha lost its ability to inhibit carrageenan-induced local inflammation and allogenic cell-induced T cell proliferation and cytokine production in vivo. Thus, the Sushi domain is critical for the functional activity of sIL-15Ralpha.

Acute Disease↗
PubMed2001

[Comparative epidemiological study on thyroid cancer in areas with different iodine intakes].

OBJECTIVE: To investigate the status of thyroid cancer among people aged 14 and over residing in areas with different iodine intakes. METHODS: In-door interviews on prevalence of thyroid cancer were conducted among 22 976 persons aged 14 and over residing in three rural communities in Panshan County, Liaoning Province, an iodine deficient area, Zhangwu County, Liaoning Province, an iodine sufficient area, and Huanghua County, Hebei Province, an iodine excessive area. Morning fasting urine, drinking water and table salt were collected from part of the interviewees to be tested. RESULTS: The medians of urinary iodide were 103.2 microgram/L, 374.8 microgram/L and 614.6 microgram/L among the interviewees in Panshan, Zhangwu and Huanghua respectively. No patient with thyroid cancer was found in Panshan and Zhangwu, while 10 interviewees in Huanghua were suffering from thyroid papillary carcinoma. During the period of 1994 - 2000, the prevalence of thyroid cancer was 91.58/100 000, and the incidence was 13.12/100 000 per year in Huanghua. CONCLUSION: The prevalence and incidence of thyroid cancer in iodine excessive area are much higher than those in the other two areas.

Adolescent↗
PubMed2001

The role of ICAM-1 molecule in the migration of Langerhans cells in the skin and regional lymph node.

ICAM-1 (CD54) plays an important role in the cell-cell interaction and migration of leukocytes. Previous studies have shown that ICAM-1 is involved in inflammatory reactions and that a defect in ICAM-1 gene inhibits allergic contact hypersensitivity. This study indicates that the migration of hapten presenting Langerhans cells into the regional lymph nodes was significantly reduced in ICAM-1-deficient mice compared to wild-type C57BL/6 mice. The reduced number of dendritic cells in regional lymph nodes did not result from abnormal migration of Langerhans cells into the skin of ICAM-1-deficient mice. The concentration and distribution of Langerhans cells in the naïve skin of ICAM-1-deficient mice was equal to that of wild-type mice. Following hapten sensitization, Langerhans cell migration out of the skin and recruitment of fresh Langerhans cells back to the epidermis was not affected in ICAM-1-deficient mice. Further experiments demonstrated that ICAM-1 deficiency on lymphatic endothelium rather than on dendritic cells was responsible for the reduced migration of Langerhans cells into draining lymph nodes. This study indicates that ICAM-1 regulates the migration of dendritic cells into regional lymph nodes but not into or out of the skin.

Animals↗
PubMed2001

Chitosan as a nonviral gene delivery system. Structure-property relationships and characteristics compared with polyethylenimine in vitro and after lung administration in vivo.

Chitosan is a natural cationic linear polymer that has recently emerged as an alternative nonviral gene delivery system. We have established the relationships between the structure and the properties of chitosan-pDNA polyplexes in vitro. Further, we have compared polyplexes of ultrapure chitosan (UPC) of preferred molecular structure with those of optimised polyethylenimine (PEI) polyplexes in vitro and after intratracheal administration to mice in vivo. Chitosans in which over two out of three monomer units carried a primary amino group formed stable colloidal polyplexes with pDNA. Optimized UPC and PEI polyplexes protected the pDNA from serum degradation to approximately the same degree, and they gave a comparable maximal transgene expression in 293 cells. In contrast to PEI, UPC was non toxic at escalating doses. After intratracheal administration, both polyplexes distributed to the mid-airways, where transgene expression was observed in virtually every epithelial cell, using a sensitive pLacZ reporter containing a translational enhancer element. However, the kinetics of gene expression differed - PEI polyplexes induced a more rapid onset of gene expression than UPC. This was attributed to a more rapid endosomal escape of the PEI polyplexes. Although this resulted in a more efficient gene expression with PEI polyplexes, UPC had an efficiency comparable to that of commonly used cationic lipids. In conclusion, this study provides insights into the use of chitosan as a gene delivery system. It emphasises that chitosan is a nontoxic alternative to other cationic polymers and it forms a platform for further studies of chitosan-based gene delivery systems.

Cell Line↗
PubMed2001

Expression of myogenic constrictor tone in the aorta of hypertensive rats.

We investigated the effect of intraluminal pressure or stretch on the development of tone in the descending thoracic aorta from rats with aortic coarctation-induced hypertension of 7-14 days duration. Increments of pressure >100 mmHg decreased the diameter of thoracic aortas from hypertensive but not from normotensive rats. The pressure-induced constriction was not demonstrable in vessels superfused with calcium-free buffer. Stretched rings of aorta from hypertensive rats exhibited a calcium-dependent constrictor tone accompanied by elevated calcium influx that varied in relation to the degree of stretch. Blockers of L-type calcium channels and inhibitors of protein kinase C reduced both basal tone and calcium influx in aortic rings of hypertensive rats. Hence, the thoracic aorta of hypertensive rats expresses a pressure- and stretch-activated constrictor mechanism that relies on increased calcium influx through L-type calcium channels via a protein kinase C-regulated pathway. The expression of such a constrictor mechanism is suggestive of acquired myogenic behavior.

Animals↗
PubMed2001

[An epidemiological survey of thyroid disorders in an area with high iodine content in water supply].

OBJECTIVE: To investigate the status of thyroid disorders among people aged 14 years and older residing in Huanghua County, an iodine excess intake area in north China. METHODS: 4,230 people were asked to fulfill the questionnaire and 1,074 among them aged (36.97 +/- 12.83) years were accepted to be samples for the test. All subjects who were taken as samples needed to fill the questionnaire on thyroid disorders in detail, accept physical and ultrasound examination. Their morning fasting urine were collected for measurement of iodide concentration, and their sera were measured for thyroid-stimulating hormone(TSH, the third generation), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb) and thyroglobulin (TG). If some people had abnormal TSH level, their free T4, free T3 and TSH receptor antibody(TRAb) were measured. RESULTS: The median level of urinary iodide of the sample subjects was 614.61 micrograms/L. The prevalence of clinical and subclinical hyperthyroidism was 1.21% and 1.12% respectively; 92.3% of the clinical hyperthyroidism were of Graves' disease and 75% of the subjects with subclinical hypothyroidism were TRAb positive. The average incidence of clinical hyperthyroidism was not different between 2 periods before and after general iodinization of table salt in this area (1991-1995 and 1996-2000). The prevalence of clinical and subclinical hypothyroidism was 1.96% and 6.05% respectively. All the clinical patients were female, among them 85.71% were TPOAb and/or TGAb positive, while only 29.23% of the subclinical patients were TPOAb and/or TGAb positive. Positive TPOAb and TGAb were seen in 11.6% and 9.3% respectively of the sample subjects with an age-related increase. Positive thyroid autoantibody was more common in the female and those with abnormal TSH. The prevalence of thyroid cancer during the period of 1994-2000 was 91.58/100,000. CONCLUSION: The high prevalence of hypothyroidism and thyroid cancer indicates that excessive iodine intake in this area is not safe.

Adult↗
PubMed2001

[Antisense monocyte chemotactic protein-1 gene inhibits vein graft intimal hyperplasia in rabbits].

OBJECTIVE: To identify the effect of in vivo local expression of recombine antisense MCP-1 gene on the development of vein graft neointima formation. METHODS: Jugular vein-to-artery bypass grafting was performed on 20 New Zealand white rabbits, of which 4 grafts were transferred with LNCX vectors, 6 grafts with antisense MCP-1 (200 micrograms) by cationic liposome, and 4 grafts as controls. Fourteen days after surgery grafts were harvested. The expression of antisense MCP-1 and its effect on MCP-1 in vein grafts were detected by dot blot. Grafts were processed for morphologic evaluation and immunohistochemistry analysis. RESULTS: Antisense MCP-1 was expressed in local gene delivery group, meanwhile MCP-1 expression in vein grafts was significantly inhibited (test group, 1.227 +/- 0.362; controls, 1.981 +/- 0.394, P < 0.05). Monocytes/macrophages adherence and infiltration were prominently reduced (test group, 24.3% +/- 2.7%; controls, 36.8% +/- 2.8%, P < 0.05), and intimal hyperplasia was markedly reduced [test group, (0.65 +/- 0.08) mm2; controls, 1.27 +/- 0.15) mm2, P < 0.05]. CONCLUSION: Local expression of antisense MCP-1 in vein graft significantly reduced intimal hyperplasia with inhibition of MCP-1 expression and prevention of monocytes/macrophages infiltration.

Animals↗
PubMed2001

[Inquiries about methods of primary eye care and prevention of blindness].

OBJECTIVE: To inquire about the methods of developing primary eye care (PEC) and prevention of blindness. METHODS: The methods of developing PEC and prevention of blindness in recent 10 years were analyzed retrospectively. RESULTS: Five grades of PEC network were established. The training courses 1 007 times were held in Nantong, and the epidemiological survey of the blind was carried out for 6 817 259 people. The blind persons were 13 496 in number, and the prevalence of blindness was 0.20%. Cataract operations were performed on 83.16% of the treatable cataract blind persons. The successful rate of cataract surgery was 98.22%. Eight counties became the national advanced counties of prevention of blindness. Nantong city became the first national advanced city of prevention of blindness in 1997. CONCLUSIONS: PEC is the basis of prevention of blindness. To bring PEC into line with the primary health care (PHC) is the key point of developing PEC. Affordable operation, promising quality of the operative procedure and combination of survey and treatment are the three essential factors of developing PEC and prevention of blindness. To create national advanced county and city is the motive force of developing prevention of blindness.

Adult↗
PubMed2001

[The significance of thrombosis after experimental pulmonary thromboembolism].

OBJECTIVE: To study the significance of thrombosis after experimental pulmonary thromboembolism (PTE). METHODS: Acute PTE models of rabbits were established with injection of autologous blood clots (0.04 g/kg) stabilized in a temperature-controlled (70 degrees C) of distilled water for 10 minutes through the femoral vein, then the regulation of thrombosis was explored at dissection and upon microscopic examination after PTE. Moreover, the coagulability of blood and the plasma level of thromboxane A2(TXA2) and endothelin (ET) were examined. RESULTS: Thrombotic propensity was found at 1 h, and fresh thrombosis started to form at 24 h following clots infusion. Emboli were completely or partly dissolved at 5 d and organized at 10 and 14 d after clots infused. Prothrombin time was significantly lower [(7.15 +/- 0.06)s], and fibrinogen was higher [(5.86 +/- 1.50) g/L] at 24 h post-clots, compared with pre-clots [(7.34 +/- 0.19)s, (3.37 +/- 1.02) g/L] (P < 0.05). Venous plasma level of TXA2 began to increase at 5 min [(2.5 +/- 0.7) micrograms/L] and continued to rise to its maximum at 15 min [(2.5 +/- 0.6) micrograms/L], then declined at 60 min after clots infusion. The level of ET in both arterial and venous blood increased at 5 d post-clots [(0.84 +/- 0.15) micrograms/L and (0.23 +/- 0.05) micrograms/L] separately, while most of emboli resolved. CONCLUSIONS: There is thrombus formation after autologous-blood-clots-induced PTE. Furthermore, thrombus formation, fibrinolysis and organization may always interact on each other consistently, and control the pathogenesis of PTE. Abnormalities of ET metabolism occur after PTE and the major mediator of TXA2 plays an important role in the early phase of PTE.

Animals↗
PubMed2001

[Fractionated-clamping for thoracoabdominal aortic aneurysm repair: report of 13 cases].

OBJECTIVE: Fractionated-clamping was applied to aneurysm repair in patients with thoracoabdominal aortic aneurysm(TAA), and its effects in decreasing operative mortality and severe complications such as renal failure and hemiplegia were discussed. METHODS: Using improved shunting and cross-clamping technique, we repaired 13 thoracoabdominal aortae and their branches (9 males and 4 females). TAA Crawford type: type I one case, type II two cases, type III two cases and type IV three cases. TAA dissection Debakey type: type I one case, type III four cases (including 2 of ruptured aneurysm) and aorta stenosis one case. RESULTS: Twelve procedures were performed successfully. One patient died of cardiac attack immediately before accomplishment of the operation with a operative mortality rate of 7.7% (1/13). Operative complications included acute necrotizing pancreatitis (1 case), ARDS (1), thoracic cavity bleeding (2), hemiplegia (1), and acute renal failure (1). The incidence rate of complications was significantly lower than that reported elsewhere. CONCLUSIONS: Fractionated-clamping for thoracoabdominal aortic aneurysm repair is a renovation on the basis of Crawford procedure and aorta bypass method. Clinical results demonstrated that the procedure decreases the surgical mortality and the incidence rate of dangerous complications. Fractionated clamping for aorta replacement is a reasonable procedure under general anesthesia at normal temperature.

Acute Kidney Injury↗
PubMed2001

Combined intraoperative iliac artery stents and femoro-popliteal bypass for multilevel atherosclerotic occlusive disease.

OBJECTIVE: To review our preliminary experience and evaluate our early results of a combined intraoperative iliac angioplasty and stenting with infrainguinal revascularization in multilevel atherosclerotic occlusive disease. METHODS: From July 1999 to April 2000, intraoperative iliac angioplasty and stenting combined with simultaneous femoro-popliteal bypass were performed on 12 lower extremities of 10 patients suffering from multilevel atherosclerotic occlusive disease. There were 8 men and 2 women, average 72 years. The indications for procedures included disabling claudication in 3 and rest pain in 7 patients. RESULTS: Eleven iliac angioplasty and stent procedures combined with simultaneous 9 femoro-popliteal by-pass and 3 femoro-femoral-popliteal bypass were performed in 12 limbs of 10 patients. Angioplasty and stent placement was technically successful in all patients. One contralateral femoral-popliteal bypass was failure after femoro-femoral-popliteal bypass. There were no additional instances of procedural or postoperative morbidity or mortality. Mean follow-up was 5 months (range 1 approximately 10 months). During the follow-up period, one femoro-infrapopliteal graft became occluded after 7 months and above-knee amputation was required. The cumulative primary patency rate of stented iliac arteries, femoro-femoral bypass grafts and femoro-popliteal bypass grafts were 100% (11/11), 100% (3/3) and 90.9% (10/11) in the follow-up period, respectively. The amputation rate was 8.3% (1/12). CONCLUSIONS: Intraoperative iliac artery PTA and stent placement can be safely and effectively performed simultaneously with infrainguinal revascularization for multilevel atherosclerotic occlusive disease by skilled vascular surgeon, using a portable C arm fluoroscopy inthe operating room. Furthermore, iliac artery PTA and stenting was valuable adjunct to distal bypass either to improve inflow and outflow, or to reduce the extent of traditional surgical intervention, and also, any angioplasty and stenting-related complications can be immediately corrected as well.

Aged↗
PubMed2000

Polymerization of nontemplate bases before transcription initiation at the 3' ends of templates by an RNA-dependent RNA polymerase: an activity involved in 3' end repair of viral RNAs.

The 3' ends of RNAs associated with turnip crinkle virus (TCV), including subviral satellite (sat)C, terminate with the motif CCUGCCC-3'. Transcripts of satC with a deletion of the motif are repaired to wild type (wt) in vivo by RNA-dependent RNA polymerase (RdRp)-mediated extension of abortively synthesized oligoribonucleotide primers complementary to the 3' end of the TCV genomic RNA. Repair of shorter deletions, however, are repaired by other mechanisms. SatC transcripts with the 3' terminal CCC replaced by eight nonviral bases were repaired in plants by homologous recombination between the similar 3' ends of satC and TCV. Transcripts with deletions of four or five 3' terminal bases, in the presence or absence of nonviral bases, generated progeny with a mixture of wt and non-wt 3' ends in vivo. In vitro, RdRp-containing extracts were able to polymerize nucleotides in a template-independent fashion before using these primers to initiate transcription at or near the 3' end of truncated satC templates. The nontemplate additions at the 5' ends of the nascent complementary strands were not random, with a preference for consecutive identical nucleotides. The RdRp was also able to initiate transcription opposite cytidylate, uridylate, guanylate, and possibly adenylate residues without exhibiting an obvious preference, flexibility previously unreported for viral RdRp. The unexpected existence of three different repair mechanisms for TCV suggests that 3' end reconstruction is critical to virus survival.

Base Pairing↗
PubMed2000

Involvement of conserved aspartate and glutamate residues in the catalysis and substrate binding of maize starch synthase.

Chemical modification of maize starch synthase IIb-2 (SSIIb-2) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC), which modifies acidic amino acid residues, resulted in a time- and concentration-dependent inactivation of SSIIb-2. ADPGlc was found to completely protect SSIIb-2 from inactivation by EDAC. These results suggest that glutamate or aspartate is important for SS activity. On the basis of the sequence identity of SS, conserved acidic amino acids were mutagenized to identify the specific amino acid residues important for SS activity. Three amino acids (D21, D139, and E391) were found to be important for SS activity. D21N showed 4% of the wild-type enzyme activity and a 10-fold decrease in the affinity for ADPGlc, while the conservative change from D21 to E resulted in a decrease in V(max) and no change in affinity for ADPGlc, suggesting that the negative charge is important for ADPGlc binding. When sites D139 and E391 were changed to their respective amide form, no SS activity was detected. With the conservative change, D139E showed a decrease in V(max) and no changes in apparent K(m) for substrates. E391D showed a 9-fold increase in K(m) for ADPGlc, a 12-fold increase in apparent K(m) for glycogen, and a 4-fold increase in apparent K(m) for amylopectin. The circular dichroism analysis indicates that these kinetic changes may not be due to a major conformation change in the protein. These results provide the first evidence that the conserved aspartate and glutamate residues could be involved in the catalysis or substrate binding of SS.

Amino Acid Sequence↗
PubMed2000

Analysis of cis-acting sequences involved in plus-strand synthesis of a turnip crinkle virus-associated satellite RNA identifies a new carmovirus replication element.

Satellite RNA C (satC) is a 356-base subviral RNA associated with turnip crinkle virus (TCV). A 3'-proximal element (3'-UCCCAAAGUAU) located 11 bases from the 3' terminus of satC minus strands can function as an independent promoter in an in vitro RNA-dependent RNA polymerase (RdRp) transcription system. Furthermore, in the absence of a 5'-proximal element, the 3'-proximal element is required for complementary strand synthesis in vitro. Site-directed mutagenesis was conducted to investigate the functional significance of this element and the 3' minus-strand terminal sequence "3'-OH-CCCUAU," which contains the minus-strand 3'-end sequence "3'-OH-CC(1-2)(A/U)(A/U)(A/U)" found in all carmovirus RNAs. Single mutations in the 3'-terminal sequence, which we have named the carmovirus consensus sequence (CCS), suppressed satC plus-strand synthesis to undetectable levels in protoplasts while still permitting some minus-strand synthesis. However, single and multiple mutations introduced into the 3'-proximal element had little or no effect on satC accumulation in protoplasts. In vivo genetic selection (SELEX) of the minus-strand 3'-terminal 21 bases revealed that all satC species accumulating in plants contained the 3' CCS. In addition, the 3'-proximal element preferentially contained a sequence similar to the CCS and/or polypurines, suggesting that this element may also contribute to accumulation of satC in vivo.

Brassica↗
PubMed2000

Requirement of a 5'-proximal linear sequence on minus strands for plus-strand synthesis of a satellite RNA associated with turnip crinkle virus.

Viral RNA replication begins with specific recognition of cis-acting RNA elements by the viral RNA-dependent RNA polymerase (RdRp) and/or associated host factors. A short RNA element (3'-AACCCCUGGGAGGC) located 41 bases from the 5' end of minus strands of satellite RNA C (satC), a 356-base subviral RNA naturally associated with turnip crinkle virus (TCV), was previously identified as important for plus-strand synthesis using an in vitro RdRp assay (H. Guan, C. Song, A. E. Simon, 1997, RNA 3, 1401-1412). To examine the functional significance of this element in RNA replication, mutations were introduced into the consecutive C residues in the element. A single mutation of the 3'-most C residue resulted in undetectable levels of satC plus strands when transcripts were assayed in protoplasts and suppressed transcription directed by the element in vitro. However, satC minus strands were detectable at 6 h postinoculation (hpi) of protoplasts, accumulating to about 10% of wild-type levels at 24 hpi. This mutation, when in the plus-sense orientation, had little or no effect on minus-strand synthesis from full-length satC plus strands in vitro, suggesting that the 5'-proximal RNA element is required for satC plus-strand synthesis. In addition, in vivo genetic selection revealed a strict requirement for 10 of the 14 nucleotides of the element, indicating that the primary sequence is essential for RNA accumulation.

5' Untranslated Regions↗