DNA polymerase potentials of sea urchin embryos

Cell-free cytoplasmic polyadenylation of oogenic RNA

The products of cell-free ATP incorporation mediated by cytoplasmic fractions prepared from unfertilized sea urchin eggs, anucleate egg halves, nucleate egg halves, emetine-treated fertilized eggs, and four-cell embryos have been characterized to determine to what extent the polymers synthesized are poly(A) and to assess the size distribution of the primers adenylated. As judged by alkaline lability, ribonuclease resistance, and retention on poly(U)-impregnated filters, greater than 92% of the label recovered after RNA extraction is present in poly(A). LiCl fractionation indicates that little, if any, free poly(A) is synthesized or cleaved from RNA primers during the reaction, and that 4S RNA is not an effective initiator. In excess of 85% of the poly(A) is associated with RNA having S-values greater than or equal to 18S. Sedimentation profiles of RNA adenylated in the unfertilized egg and anucleate egg half reactions are identical. Suppression of in vivo protein synthesis by emetine alters the profile of RNA subsequently adenylated in vitro. It is proposed that the apparent constraints on the utilization of cytoplasmic RNA or ribonucleoprotein primers of oogenic origin may be effected by RNA-associated proteins capable of regulating the selection and/or extent of their polyadenylation during early embryogenesis.

Characterization of an alpha-like DNA polymerase from Bombyx mori silkglands

A soluble DNA polymerase has been purified near to homogeneity from Bombyx mori silkglands. The following characteristics were observed: high molecular weight (about 150 000 - 220 00); optimum pH about 8; inhibition by high salt concentrations, sulfhydryl-group blocking agents and polyamines; absence of nuclease activity; preference for magnesium as required divalent cation with all the efficient template-primers tested; and clear template-primer specificity, the purified enzyme being able to copy primed - polydeoxyribonucleotide templates [activated DNA, poly(dA).oligo(dT), poly(dA).oligo(rU)] but not polyribonucleotide chains [poly(rA).oligo(dT), poly(rA).oligo(rU)] in the presence of either Mg++ or MN++. Believed to represent the bulk of silkgland DNA polymerase activity, the purified soluble enzyme most resembles vertebrate DNA polymerases alpha when it is compared to other eukaryotic DNA polymerases as yet characterized.

Partial purification and characterization of two cytoplasmic DNA polymerases from ungerminated wheat

Two DNA polymerases have been purified from the 105,000 x g supernatant of ungerminated wheat. The purification stages included: high speed centrifugation, salt fractionation, DEAE-cellulose chromatography, Sephadex G-150 filtration and phosphocellulose chromatography. Several properties of the two enzyme (called A and B according to the order of elution from the phosphocellulose column) have been studied. Enzyme A has a sedimentation coefficient of about 7 S, utilizes activated DNA and synthetic polydeoxynucleotides as well as poly rA-dT12, while B has a sedimentation coefficient of about 6.2 and uses only activated DNA and synthetic polydeoxynucleotides as templates. Other parameters like KCl effect, MnCl2 effect, optimum pH, etc. Allow us to distinguish clearly between both DNA polymerases.

Polyadenylylation and transcription following fertilization

Polyadenylylated RNA from sea urchin embryos concomitantly labeled with [(3)H]adenosine and [(14)C]uridine between fertilization and the four-cell stage was used to determine whether the RNA primers prerequisite to the massive polyadenylylation known to occur after fertilization are synthesized during oogenesis or subsequent to fertilization. Characterization of this RNA and unlabeled RNA via retention on nitrocellulose membranes and poly(U)-impregnated filters, molecular hybridization with [(3)H]poly(U), RNase resistance, oligo(dT)-cellulose chromatography, and size-distribution studies indicates that the poly(A) tracts synthesized after fertilization are predominantly appended to preexisting cytoplasmic primers of oogenic origin. Hence, if polyadenylylation is involved in the selective editing of presumptive genetic messages, this process is not confined to the nucleus unless a given codogenic transcript can undergo more than one cycle of adenylylation.

Multiple forms of DNA polymerase in mouse myeloma

FIVE DISTINCT FORMS OF DNA POLYMERASE (DEOXYNUCLEOSIDETRIPHOSPHATE: DNA deoxynucleotidyltransferase, EC 2.7.7.7) were separated from extracts of mouse myeloma MOPC-104E using a fractionation procedure based upon sequential ion-exchange column chromatography. The enzymes were characterized according to sedimentation behavior, subcellular localization, chromatographic behavior on hydroxyapatite columns, and reaction properties. The results indicate that myeloma contains two enzymes that appear to correspond to well characterized DNA polymerases found in many other mammalian tissues, a 6S DNA polymerase localized in the cytoplasmic supernatant fraction, and a lower molecular weight (2-3S) DNA polymerase. Also present were a second 6S DNA polymerase localized exclusively in the nuclear fraction and a 6-8S DNA polymerase localized in the cytoplasmic membrane fraction. The enzyme in the cytoplasmic membrane fraction, which accounted for the predominant activity in the myeloma, was active with poly(rA).(dT)(12-18) as template-primer, but not with activated calf thymus DNA. The detection of this distinct 6-8S membrane-bound DNA polymerase is of particular interest.

Cytoplasmic adenylylation and processing of maternal RNA

Molecular hybridization between [(3)H]-poly(U) and unlabeled RNA prepared from sea urchin eggs and embryos has been used to contrast the subcellular localization as well as the size distribution of adenylylated maternal RNA preexisting in the unfertilized egg with that adenylylated as a function of fertilization. Evidence reported establishes that such preadenylylated genetic messages are predominantly located in the ovum's subribosomal fraction and that fertilization elicits a rapid reallocation of these latent transcripts into the zygote's ribosomal fraction. Examination of the size distribution of the adenylylated RNA further demonstrates that the unfertilized egg contains a substantial population of RNA transcripts of exceptionally high molecular weight that are used as primers for the 2-fold net synthesis of poly(A) that follows fertilization. The poly(A)-rich tracts are shown to be covalently bonded to RNA. Assessment of the poly(A) content of nuclear and cytoplasmic fractions suggests that the function of poly(A) is not confined to the transport of genetic messages from the nucleus.

DNA-dependent DNA polymerases I and II from normal human-blood lymphocytes

Two DNA polymerases have been purified from blood lymphocytes of normal human individuals. In contrast to a DNA polymerase isolated from lymphoblasts from individuals with leukemia, neither of the DNA polymerases from normal lymphocytes transcribes the heteropolymeric regions of tumor-virus RNA into DNA.