Components required for in vitro cleavage and polyadenylation of eukaryotic mRNA

We have studied in vitro cleavage/polyadenylation of precursor RNA containing herpes simplex virus type 2 poly A site sequences and have analyzed four RNA/protein complexes which form during in vitro reactions. Two complexes, A and B, form extremely rapidly and are then progressively replaced by a third complex, C which is produced following cleavage and polyadenylation of precursor RNA. Substitution of ATP with cordycepin triphosphate prevents polyadenylation and the formation of complex C however a fourth complex, D results which contains cleaved RNA. A precursor RNA lacking GU-rich downstream sequences required for efficient cleavage/polyadenylation fails to form complex B and produces a markedly reduced amount of complex A. As these GU-rich sequences are required for efficient cleavage, this establishes a relationship between complex B formation and cleavage/polyadenylation of precursor RNA in vitro. The components required for in vitro RNA processing have been separated by fractionation of the nuclear extract on Q-Sepharose and Biorex 70 columns. A Q-Sepharose fraction forms complex B but does not process RNA. Addition of a Biorex 70 fraction restores cleavage activity at the poly A site but this fraction does not appear to contribute to complex formation. Moreover, in the absence of polyethylene glycol, precursor RNA is not cleaved and polyadenylated, however, complexes A and B readily form. Thus, while complex B is necessary for in vitro cleavage and polyadenylation, it may not contain all the components required for this processing.

Sedimentation analysis of polyadenylation-specific complexes

Precursor RNA containing the adenovirus L3 polyadenylation site is assembled into a 50S complex upon incubation with HeLa nuclear extract at 30 degrees C. The cofactor and sequence requirements for 50S complex formation are similar to those of the in vitro polyadenylation reaction. Assembly of this complex requires ATP but is not dependent upon synthesis of a poly(A) tract. In addition, a 50S complex does not form on substrate RNA in which the AAUAAA hexanucleotide upstream of the poly(A) site has been mutated to AAGAAA or on RNA in which sequences between +5 and +48 nucleotides downstream of the site have been removed. These mutations also prevent in vitro processing of substrate RNA. Kinetic studies suggest that the 50S complex is an intermediate in the polyadenylation reaction. It forms at an early stage in the reaction and at later times contains both poly(A)+ RNA as well as unreacted precursor. U-type small nuclear ribonucleoprotein particles are components of the 50S complex, as shown by immunoprecipitation with antiserum specific to the trimethyl cap of these small nuclear RNAs.

Electrophoretic separation of polyadenylation-specific complexes

A polyadenylation-specific complex composed of precursor RNA containing the adenovirus-2 L3 site and HeLa cellular components was detected by electrophoresis on a native, low-percentage polyacrylamide gel. Upon incubation in a reaction containing ATP and nuclear extract, precursor RNA was rapidly assembled into this complex. This assembly did not require poly(A) synthesis, as it occurred efficiently in the presence of ATP analogs that inhibited this reaction. Mutation of the hexanucleotide AAUAAA 20 nucleotides upstream of the L3 site to AAGAAA or deletion of sequence between +5 and +48 nucleotides downstream of the L3 site inactivates polyadenylation. The specific complex did not effectively from on substrate RNA with either the AAGAAA mutation or the downstream deletion mutation. Kinetic experiments showed that the assembly of this complex preceded processing of precursor RNA. We proposed that formation of this complex represents an intermediate step in polyadenylation.

Behavioral responses of infant rats to maternal licking: variations with age and sex

Behavioral interactions of Norway rat pups and their dams during maternal anogenital licking (AGL) were observed. Regularities in posture and orientation that may facilitate AGL were noted, and age-related changes in the pup's postural adjustments that may contribute to the decline of AGL in the 3rd postpartum week were described. It was found that cutaneous stimulation of the perineum, such as that provided by AGL, stimulates a characteristic leg extension response from pups. It was concluded that this response, which includes immobility and extension of all limbs, may permit maternal licking to continue long enough to stimulate the pup to eliminate and to allow the dam to ingest the urine. Males and females were found to exhibit similar responses and similar age-related changes. However, the latency from onset of AGL to performance of the leg extension response was shorter in males.

Analysis of RNA cleavage at the adenovirus-2 L3 polyadenylation site

Processing at the L3 polyadenylation site of human adenovirus-2 involves endonucleolytic cleavage generating the 3' terminal sequence -UAOH to which adenosine residues are added. This dinucleotide is 19 nucleotides downstream of the AAUAAA polyadenylation signal. The ATP analog cordycepin triphosphate (3' dATP) inhibits poly(A) synthesis, but precursor RNA is processed to give a product terminating in -UAAH. Addition of only one adenosine analog demonstrates that the initial poly(A) tract is synthesized by polymerization of single residues rather than by ligation of preformed poly(A). Cleavage is not coupled to polyadenylation since incubation with an ATP analog containing a non-hydrolyzable alpha--beta bond generates a product with a 3' terminus coincident with the -UAOH) addition site. Addition of this accurately processed RNA to a nuclear extract results in efficient polyadenylation, suggesting that downstream sequences are not required for synthesis of the poly(A) tract. Finally, processing at the L3 poly(A) site may involve both endonucleolytic and exonucleolytic activities.

A hormonal basis for sex differences in the self-grooming of rats

The self-grooming behavior of prepubescent male and female rats is described. Sex differences were observed in components of grooming addressed to the genitals, but not in other aspects of grooming. A hormonal basis for the sex difference was examined in two experiments. When females were injected with testosterone propionate (TP) on the day of birth, their subsequent grooming was found to be no different from that of control-treated females. However, males and females gonadectomized at weaning and treated daily with TP each performed significantly more genital self-grooming than oil-treated controls. There were no sex differences in gonadectomized, oil-treated rats, and sex differences in response to TP were limited to greater responsiveness of females to a 50-micrograms, but not 200-micrograms, TP dose. These results lead to the conclusion that sex differences in self-grooming can be accounted for primarily by differences in testosterone availability during the peripubertal period.

Prenatal stress affects mother-infant interaction in Norway rats

Pregnant Long-Evans rats were stressed by crowding, and subsequent mother-infant interactions were described after cross-fostering. Prenatally stressed pups elicited less maternal licking from unstressed foster dams than controls, and previously stressed dams licked unstressed foster pups less than controls. No other differences in mother-infant interactions were detected. Adult offspring reared by foster dams that were stressed during pregnancy were more active in an open field than controls, but prenatally stressed and unstressed animals reared by control dams did not differ. Thus, stress during pregnancy can alter the maternal behavior of stressed dams, and the differential maternal stimulation can affect adult open-field behavior. Because prenatally stressed pups elicit different maternal care, cross-fostering does not eliminate the possibility that maternal stimulation may mediate some prenatal stress effects.

Depletion of brain mitochondria cytochrome oxidase in the mottled mouse mutant

The mouse mutant Mobr is an animal model of Menkes kinky hair syndrome with a similar defect in copper utilization. The copper-dependent enzyme, cytochrome oxidase from the brain, liver, and heart mitochondria was examined. The brain and heart from Mobr/y had significantly less cytochrome alpha + alpha 3 than normal animals' when the cytochrome absorption spectra of tissue samples from animals 11 to 13 days of age were analyzed. Liver cytochrome was not significantly different. When brain mitochondrial cytochrome oxidase spectrograms from animals of different ages were examined, a major change was found to occur during the 2nd week of life. When cytochrome oxidase activity from brain mitochondria was measured, assaying the rate of oxidation of cytochrome c, the results were similar to those from spectrogram analysis.

Sex differences in self-grooming of rats: effects of gonadal hormones and context

When prepubescent males and females were placed alone in a novel cage, males were found to groom their genitals, but not other body regions, more than females. This sex difference was present in untreated and in testosterone-treated gonadectomized rats as well as in intact rats. Neither the presence of gonads nor testosterone treatment affected grooming in this context. However, when similarly treated rats of the same age were observed in groups in the home cage, no sex difference in genital grooming of intact or gonadectomized rats was found. Testosterone significantly increased nongenital grooming in both sexes and genital grooming in males. Thus, both the presence of sex differences and the effects of testosterone on self-grooming depend on the behavioral context.

Prenatal stress eliminates differential maternal attention to male offspring in Norway rats

Maternal licking behavior was observed in 20 Long-Evans rat dams on two consecutive days. Stimulus pups were male and female foster pups from dams that were either housed with 5 adult males during the last trimester of pregnancy (stressed) or housed alone (unstressed). Unstressed male pups received significantly more maternal licking than their female siblings, but prenatally stressed males and females received similar levels of maternal licking, comparable to that directed to unstressed females. In a second study, urine collected from prenatally stressed male pups elicited significantly less investigation from dams in a choice test than urine from age-matched unstressed males. It is concluded that the chemosignals which stimulate dams normally to provide more maternal attention to male than female neonates are deficient in prenatally stressed males. The results raise the possibility that differential maternal care may mediate some effects of prenatal stress on behavioral development in males.

Contribution of nesting experience to progesterone-induced incubation in ring doves (Streptopelia risoria)

Injections of progesterone induce incubation behavior in gonadally intact ring doves only if the doves have had previous experience with at least the nest-building phase of a breeding cycle. The present study was designed to determine whether exposure to progesterone during the nest-building phase is sufficient to account for the ability of progesterone to induce incubation at a later time or whether some other factor provided by experience with this phase of the cycle is needed. Six groups of 10 pairs of doves each were provided with different combinations of experience and progesterone priming. Progesterone priming combined with social isolation or with courtship experience had no significant effect on subsequent progesterone-induced incubation. However, doves that participated in the nesting phase of the cycle during progesterone priming later incubated in response to progesterone treatment. Nesting activity, which may or may not include building the nest, seemed to be the relevant experience.

Sex differences in urinary odors produced by young laboratory rats (Rattus norvegicus)

Responses of adult female rats to male and female pup urine were examined in three experiments. Investigatory sniffing of male and female pup urine deposits by maternal rats was compared in a series of simultaneous choice tests given at 3-day intervals between Day 2 and Day 17 postpartum. Male urine was consistently preferred. Introduction of male, but not female, pup urine to the nest was also found to significantly elevate maternal licking of anogenital regions of pups. Thus, urine from pups of various ages contains sex-identifying odors that differentially elicit spontaneous maternal interest. The odor of male urine may provide a sufficient stimulus to account for the greater anogenital licking that males of this species normally receive. Nonmaternal, naive, adult females behaved like maternal rats, preferring male urine in the choice test. This indicates that the maternal condition of a dam is not necessary either for the olfactory discrimination or for the male odor preference.

Accurate cleavage and polyadenylation of exogenous RNA substrate

Purified precursor RNA containing the L3 polyadenylation site of late adenovirus 2 mRNA is accurately cleaved and polyadenylated when incubated with nuclear extract from HeLa cells. The reaction is very efficient; 75% of the precursor is correctly processed. Cleavage is rapidly followed by polymerization of an initial poly(A) tract of approximately 130 nucleotides. Additional adenosine residues are added during further incubation. In the presence of the ATP analog alpha-beta-methylene-adenosine 5' triphosphate, the precursor RNA is cleaved but not polyadenylated, suggesting that processing is not coupled to the synthesis of the initial poly(A) tract. In the absence of free Mg2+, a small RNA of approximately 46 nucleotides is stabilized against degradation. Fingerprint analysis suggests this RNA is produced by endonucleolytic cleavage at the L3 site. Like the in vitro splicing reaction, the in vitro polyadenylation reaction is inhibited by adding antiserum against the small nuclear ribonucleoprotein particle containing U1 RNA.

Maternal contributions to the development of masculine sexual behavior in laboratory rats

Maternal licking was manipulated by lining the nasal passages of rat dams with polyethylene tubing to interfere with their olfactory competence. Olfactory cues from pups elicit maternal licking and handling, particularly of anogenital regions, and dams with olfactory deficits were observed to lick their pups less. Mature male and female offspring of these dams and their controls were gonadectomized, treated with testosterone propionate, and tested for masculine sexual behavior. The male offspring of dams that provided less maternal licking had longer ejaculatory latencies, longer post-ejaculatory intromission latencies, and longer inter-intromission intervals than controls. Female offspring of the intubed dams performed fewer mounts and intromissions, had longer intromission latencies, and longer inter-intromission intervals. It was concluded that stimulation from maternal licking contributes toward the development of a mechanism that underlies the timing of copulatory rate.

The importance of immunologic factors in the pathogenesis of encephalomyocarditis virus induced diabetes in mice

The pathogenesis of EMC virus induced diabetes has generally been thought to be caused by direct cytopathic effect of the virus on beta cells with susceptibility or resistance dictated primarily by the density of viral receptors on the beta cells of different individuals. The histological finding of insulitis, our demonstration of a protective effect of immunosuppression with ALS or anti-theta antibody and silica supports host immune factors as important determinants of susceptibility. A critical role of the immune system might be mediated by autoimmune destruction of EMC-virus infected beta cells. In susceptible strain mice treated with low dose cyclophosphamide to deplete suppressor cells, which may halt the autoimmune process and allow recovery, a prolonged period of hyperglycemia was demonstrated as compared to controls. Bone marrow exchanged between susceptible and resistant strains was also found to alter susceptibility. "B mice", deficient in T lymphocytes, when infected with EMC virus had a decreased incidence of diabetes. Susceptibility to EMC diabetes may be dictated by the autoaggressive response of host immune system to beta cells altered by EMC virus infection.

Contribution of self-grooming to onset of puberty in male rats

Self-grooming was observed to increase during the prepubertal period of Long-Evans rats. Males were significantly more likely than females to engage in genital grooming during this period. To determine whether self-grooming contributes to the onset of puberty, males were fitted with collars that either prevented or allowed self-grooming of hindquarters or were left uncollared from 27 to 48 or 55 days of age when autopsied to determine weight of accessory organs. Ventral, dorsal, and lateral prostates and seminal vesicles were significantly lighter in those rats wearing collars that prevented self-grooming. It was concluded that self-grooming, probably of the genitals, contributes to accessory organ growth in males of this species.

Site-specific polyadenylation in a cell-free reaction

A soluble HeLa cell extract accurately polyadenylates RNA transcribed from DNA templates containing the adenovirus L3 polyadenylation site. Regardless of the length of these DNA templates, the major polyadenylated species had 3' termini corresponding to the in vivo site. Polyadenylated RNA appears after an hour lag and only reaches maximum levels after 4 hr of incubation, a time course similar to that of splicing in this extract. Inhibitor studies suggest that the polyadenylation reaction is not coupled to active transcription. Unlike splicing in this extract where exogenous substrate is processed, addition of purified RNA precursor to the reaction does not yield product polyadenylated at L3 but rather results in addition of poly (A) to termini of the precursor. This suggests that part of the specificity of polyadenylation is established by in situ synthesis of RNA. Surprisingly, synthesis of accurately polyadenylated RNA may involve small nuclear ribonucleoprotein particles (snRNPs). The reaction is inhibited by antisera of Sm and U1 RNP specificities as well as antiserum to the nuclear antigen La, but is not inhibited by control serum and anti-(U2)RNP serum.

Synergistic effect of AMP and fructose 2,6-bisphosphate on the protection of fructose 1,6-bisphosphatase against inactivation by trypsin

The rate of inactivation of chicken liver fructose 1,6-bisphosphatase by trypsin is reduced if the digestive reaction is conducted in the presence of AMP or fructose 2,6-bisphosphate. The effects of these 2 compounds are synergistic. Although fructose 1,6-bisphosphate does not protect the enzyme against tryptic inactivation, it can enhance the effect of AMP. Selective modification of the AMP allosteric site of fructose 1,6-bisphosphatase with pyridoxal-P and NaBH4 renders the enzyme more resistant to tryptic inactivation, but the modified enzyme is no longer responsive to the protective effect of AMP.

An observation about myelination

An analysis of the direction of myelination of fibers in the optic tract of a kitten shows that the direction of wrapping of neighboring fibers is not random. Adjacent fibers in contact with the same glial process tend to be wrapped in the same direction. A model for myelination is proposed to account for this observation.

Gyrase . DNA complexes visualized as looped structures by electron microscopy

Gyrase bound to duplex DNA in the absence of ATP is seen by electron microscopy as a nearly spherical particle frequently located at the intersection of two duplex DNA strands. Such looped structures with gyrase situated at the base of the loops are observed with both linear and circular DNA substrates, and two or three individual DNA molecules bound to the same protein are also seen at high DNA concentrations. Addition of the nonhydrolyzable beta,gamma-imido analog of ATP to the gyrase . DNA reaction mixture prior to sample fixation for microscopy reduces the frequency of gyrase molecules found at DNA intersections. Looped structures similar to those of the gyrase . DNA complex are also seen with the complex of DNA and the A subunit of gyrase. When negatively supercoiled DNA which has been partially relaxed by gyrase in the absence of ATP is fixed for electron microscopic examination, intermediate forms are observed that contain both supercoiled and relaxed loops in a single DNA molecule, with the enzyme located at the common base of the loops. These results suggest that gyrase possesses multiple DNA-binding sites, a feature which allows the enzyme to hold DNA in constrained loops. The relation of these observations to the mechanism of gyrase action is discussed.

Filamentous structures associated with Epstein-Barr virus-infected cells

After the onset of Epstein-Barr virus DNA and protein synthesis 10 h after superinfection of Raji cells (a cell line containing Epstein-Barr virus DNA but not producing virus), filamentous structures 25 nm in diameter and 0.2 to 1.4 micrometers in length could be detected in the cell cytoplasm by electron microscopy. These structures banded in metrizamide gradients with viral DNA and proteins, but at a density different from that of virions or nucleocapsids. These filaments, enriched in a 155,000-dalton protein similar in size to a major nucleocapsid protein of Epstein-Barr virus, may represent intermediates in viral nucleocapsid assembly.