A cell-free system for protein synthesis from newly fertilized eggs of Drosophila melanogaster

The role of dNTP metabolites in control of the embryonic cell cycle

Deoxyribonucleotide metabolites (dNTPs) are the substrates for DNA synthesis. It has been proposed that their availability influences the progression of the cell cycle during development and pathological situations such as tumor growth. The mechanism has remained unclear for the link between cell cycle and dNTP levels beyond their role as substrates. Here, we review recent studies concerned with the dynamics of dNTP levels in early embryos and the role of DNA replication checkpoint as a sensor of dNTP levels.

The expression and genomic organization of randomly selected cloned Drosophila melanogaster genes

A lambda recombinant DNA library containing Drosophila melanogaster nuclear DNA inserts was screened with cDNA made from oocyte and gastrula poly(A)+ RNA. 124 clones were isolated which represented sequences complementary to a distribution of abundancies of their RNAs. The clone set was then used as probes to identify those whose RNA abundancies changed during embryonic development. The vast majority of clones showed little difference during development. Four different clones were identified whose poly(A)+ RNAs were quantitatively regulated; two were oocyte-specific, and two were embryonic-specific. 44 clones were chosen for in situ hybridization to salivary gland polytene chromosomes. The location and distribution of their sites are described. A class of clones, identified by in situ hybridization to the nucleolus, is further described. These clones contain a scrambled array of ribosomal intervening sequences.

mRNA usage during Drosophila melanogaster embryonic development. Analysis of nine cloned DNA segments

A set of nine phage lambda clones containing inserts from Drosophila melanogaster which are complementary to cDNA made from oocyte poly(A)+ RNA were selected from a larger group. These cloned elements code for a range of middle abundant RNA sequences which show no appreciable change in abundance during Drosophila embryogenesis. Seven of the nine clones are complementary to two oocyte RNAs, one to three RNAs and one to four RNAs. This study describes the changes that occur in these RNAs during embryonic development in the polysomal and non-polysomal fraction, and in the poly(A)+ RNA and poly(A)- RNA fraction. In all nine of these clones, greater than 70% of the complementary RNA is found in the polysomal region of a sucrose gradient. This proportion increases somewhat during development. Specific changes have been found during development in the proportion of RNA that is poly(A)+. Depending to the cloned sequence, this proportion may increase, decrease, or remain unchanged. For those clones that show a change, most of this change occurs between 8 and 19 h of development. Our data suggest, furthermore, the presence of a class of non-adenylated RNA being utilized during embryogenesis.

Translation of black beetle virus RNA and heterologous viral RNAs in cell-free lysates derived from Drosophila melanogaster

A cell-free protein synthesizing system was prepared from cells of Drosophila melanogaster line 1 and made mRNA dependent by treatment with micrococcal nuclease. The system was tested with homologous RNA from black beetle virus propagated in Drosophila cells, with Drosophila heat shock mRNA, and with various heterologous viral mRNA's. Under optimal conditions amino acid incorporation programmed with black beetle virus RNAs was 30-fold higher than endogenous incorporation. RNAs 1 and 2 primarily directed the synthesis of proteins with approximately molecular weights of 120,000 and 46,000, respectively. mRNA's, prepared by transcription from vesicular stomatitis virus or vaccinia virus, were translated efficiently and yielded products that comigrated with authentic viral proteins. Brome mosaic virus RNA and encephalomyocarditis virus RNA were translated poorly. The system retained full activity after freezing.

Isolation and characterization of complementary deoxyribonucleic acid complementary to the highly abundant class of poly(adenylic acid)-containing ribonucleic acid from oocytes of Drosophila melanogaster

The complementary deoxyribonucleic acid (cDNA) complementary to the highly abundant class of poly(adenylic acid)-containing ribonucleic acid [poly(A+) RNA] from Drosophila melanogaster oocytes has been isolated and characterized. Analysis of the kinetics of hybridization of this cDNA (cDNAHA) to total poly(A+) RNA of oocytes indicates this class contains approximately 86 different sequences. Hybridization kinetics of cDNAHA annealed to poly(A+) RNA from 19-old embryos is essentially the same as that of oocyte poly(A+) RNA. This suggests the highly abundant class of poly(A+) RNA persists in approximately the same frequency through early development. Analysis of the hybridization of cDNAHA to genomic DNA suggests that the highly abundant poly(A+) RNA from oocytes is not enriched for transcripts from repetitive sequences of the genome.

Isolation and characterization of cDNA complementary to transient maternal poly(A)+ RNA from the Drosophila oocyte

cDNA complementary to total oocyte poly(A)+ RNA from Drosophila melanogaster was enriched for sequences complementary to transient maternal sequences; that is, those sequences which disappear from the oocyte during subsequent. A seven- to ten-fold enrichment factor was obtained, from 5.3% to about 50% of the total cDNA. Kinetic analysis of this enriched fraction indicates that the transient maternal sequences include 44 +/- 14 different sequences.