Hybridization analysis of histone messenger RNA: association with polyribosomes during the cell cycle.

Hybridization of cell cycle stage-specific polyribosomal RNA's to histone complementary DNA indicates that histone messenger RNA sequences are present on polyribosomes of Hela S3 cells only during the period of DNA replication.

Cytoplasmic Reversion of cms-S in Maize: Association with a Transpositional Event.

Spontaneous reversion to fertility in S male-sterile cytoplasm of maize is correlated with the disappearance of the mitochondrial plasmid-like DNA's, S-1 and S-2, and changes in the mitochondrial chromosomal DNA. Hybridization data indicate that one of the plasmid-like DNA's, S-2, is prominently involved in the mitochondrial DNA rearrangements.

Multiple forms of maize endosperm adp-glucose pyrophosphorylase and their control by shrunken-2 and brittle-2.

Heat-labile and heat stable forms of ADP-glucose pyrophosphorylase were identified in the maize endosperm. The heat-labile form is destroyed by normal electrophoretic conditions. The heat-stable form corresponds to pyrophosphorylase B. In wild type, 96% of the total activity is heat labile. Both forms are reduced in 11 brittle-2 (bt2) and 12 shrunken-2 (sh2) mutants. The heat-labile form is reduced to a greater extent than is the heat-stable form in each of the 23 mutants. Deletion of sh2 abolishes both forms. The original ratio of the two forms is restored after sh2 function is expressed via transposition of Dissociation from sh2. The possible roles of these genes in the control of ADP-glucose pyrophosphorylase are discussed.

Template requirement of maize RNA polymerase.

Maize RNA polymerase utilizes heated deoxyribonucleic acid more effectively than native deoxyribonucleic acid as a template for ribonucleic acid synthesis. A ribonucleic acid-deoxyribonucleic acid hybrid accumulates in the presence of heated deoxyribonucleic acid. The amount of product formed with either native or heat-denatured deoxyribonucleic acid does not exceed the amount of deoxyribonucleic acid added as template.

A rapid technique for the estimation of polynucleotide adenylyltransferase and ribonucleic Acid polymerase in plant tissues.

Nucleic acid-dependent polynucleotide adenylytransferase (EC 2.7.7.19) and ribonucleic acid polymerase (EC 2.7.7.6) have been partially purified from maize tissues (Zea mays L.) utilizing ammonium sulfate precipitation and batch diethylaminoethylcellulose chromatography. The technique is applicable to the simultaneous processing of up to eight samples of plant tissue and affords a rapid and reproducible means of assaying these two enzymes from small quantities of kernels or seedlings. The kinetic characteristics of the partially purified enzymes resemble those from more extensively purified preparations.

Examination of the mitochondrial genome of revertant progeny from S cms maize with cloned S-1 and S-2 hybridization probes.

We have examined the molecular rearrangement of mitochondrial DNAs in each of several fertile revertants that arose spontaneously from S-type cytoplasmically male-sterile maize. Cloned segments of S-1 and S-2 DNAs (plasmid-like DNAs characteristic of the mitochondrial DNAs of S-type lines) were hybridized to untreated and restriction endonuclease-treated mitochondrial DNAs from fertile plants carrying normal cytoplasm, from cytoplasmically male-sterile plants, and from plants that had cytoplasmically reverted to fertility. The relative intensity of hybridization with S-1 and S-2 probes was different among the fertile, sterile, and revertant lines. The sizes of some restriction endonuclease fragments from the fertile revertant lines that hybridize with the S-2 probe differ from those of the sterile parental lines. Preferential synthesis of high molecular weight components of the mitochondrial genome carrying S-1 and S-2 sequences, concomitant with cessation in apparent autonomous replication of discrete S-1 and S-2 DNAs and their replicative intermediates (described here), could accommodate the hybridization data. The results suggest but do not prove that S-2 sequences are transposed coincident with the sterile plant's reversion to fertility. The inserted segments could arise from sequences already present in the high molecular weight DNA or from the lower molecular weight linear components of the mitochondrial genome. Putative target sites of insertion of S-1 and S-2 sequences would be multiple and separate for each. Reversion of S-type cytoplasmically male-sterile plants to fertility does not restore the organization of the mitochondrial genome to that of a normal fertile plant.

Utilization of ribonucleic acid and deoxyoligomer primers for polyadenylic acid synthesis by adenosine triphosphate: polynucleotidylexotransferase from maize.

The ATP:polynucleotidylexotransferase isolated and purified from maize seedlings catalyzes the synthesis of polyadenylic acid by the sequential addition of 80 to 200 AMP moieties from ATP to the 3'-hydroxyl terminus of either ribo- or deoxyoligomers. Copurification of the RNA and DNA-primed activities, identical metal cofactor and reaction requirements for either primer and identical heat inactivation curves with either primer strongly suggest that both primers are utilized by the same enzyme.

Conservation of the primary structure at the 3' end of 18S rRNA from eucaryotic cells.

DNA sequencing methods have been used to determine a sequence of about 20 nucleotides at the 3' termini of various 18S (small ribosomal subunit) RNA molecules. Polyadenylated rRNA was first synthesized using the enzyme ATP:polynucleotidyl transferase from mainze. Then in the presence of an oligonucleotide primer uniquely complementary to the end of each adenylated rRNA, a cDNA copy was produced using AMV reverse transcriptase. In every case, the cDNA transcript was of finite size, which we ascribe to the appearance of an oligonucleotide containing m62A near the 3' end of the 18S rRNAs. Sequences at the 3' termini of 18S rRNA molecules from the four eucaryotic species examined here (mouse, silk worm, wheat embryo and slime mold) are highly conserved. They also exhibit strong homology to the 3' end of E. coli 16S rRNA. Two important differences, however, are apparent. First, the 16S sequence CCUCC, implicated in mRNA binding by E. coli ribosomes, is absent from each eucaryotic rRNA sequence. Second, a purine-rich region which exhibits extensive complementarity to the 5' noncoding regions of many eucaryotic mRNAs appears consistently.

Evidence for fidelity of chromatin reconstitution.

Several lines of evidence are presented which support the contention that chromatin may be dissociated, fractionated, and reconstituted without altering the compositional, structural, or transcriptional integrity of the genome. The similar compositions of native and reconstituted chromatins are suggested by the absence of significant differences in their protein/DNA ratios and in the polyacrylamide gel electrophoretic profiles of their histones and nonhistone chromosomal proteins. Criteria for fidelity of genome structure in reconstituted chromatin include binding of reporter molecules with specificity for the minor groove of DNA, binding of histones, number of sites available for addition of nucleotides, and circular dichroism spectra. When the transcriptional activities of native and reconstituted chromatins were compared under conditions where reinitiation is prohibited, significant changes were not observed. Taken together, the present results strongly suggest, but do not conclusively establish, fidelity of chromatin reconstitution.