Bacteriophage MS2 RNA is 3,569 nucleotides long. The nucleotide sequence has been established for the third and last gene, which codes for the replicase protein. A secondary structure model has also been proposed. Biological properties, such as ribosome binding and codon interactions can now be discussed on a molecular basis. As the sequences for the other regions of this RNA have been published already, the complete, primary chemical structure of a viral genome has now been established.

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Human fibroblast cells produce beta-type interferon only in response to viral infection or treatment with an inducer such as poly(rI) X poly(rC); this event is most probably controlled at the transcriptional level (for review see ref. 1). To study the induction process, we inserted the human fibroblast interferon (IFN-beta) gene, with or without its promoter region, into recombinant simian virus 40 (SV40) plasmid vectors which subsequently were transfected into monkey AP-8 cells. We report here that upon induction with poly(rI) X poly(rC) there was a 10-30-fold increase in IFN-beta synthesis. This inducer had no effect on interferon production when the coding region only was inserted into the vector plasmid, which indicates that the promoter region is required for inducibility of this gene. Deletion mapping implicates the region between nucleotides -144 and -186 from the mRNA initiation site in the specific regulation of the IFN-beta gene. This region contains a sequence that is remarkably homologous with a consensus sequence found in the 5' flanking region of steroid hormone responsive genes, which might be involved in binding the progesterone-receptor complex.

Southern hybridization using 32P‐labelled human interleukin 2 (IL2) cDNA probes revealed the existence of a single human IL2 gene. Five clones containing the human IL2 chromosomal gene were isolated from two different human DNA libraries cloned in either lambda Charon 4A or L47 phages. Analysis of the clones showed that they contained different, overlapping portions of human DNA which were derived from the same chromosomal segment. Restriction fragments which hybridized with labelled IL2 cDNA probes were subcloned into plasmid pUR250 and the sequence and organization of the IL2 gene was determined. It contains three introns, 90 bp, +/‐ 2400 bp and +/‐ 1900 bp in length, respectively. The organization of the genomic clone resembles that of another lymphokine, interferon‐gamma, but no clear homology was found by comparing either the coding sequence or the 5′‐ and 3′‐flanking sequences of the two genes.

Simian virus 40 mutants were constructed with deletions at the late side of the origin of DNA replication by partial Bal 31 digestion at the SphI site or at the PvuII site. Some of these mutants lost virtually all of both 72-base-pair repeat segments ("enhancer" sequences) and exhibited a decrease in viability from 20to 300-fold; one particular mutant, d11852, even showed a reduction of almost 104fold. The very poorly growing deletion mutants were unstable and gave rise to DNA rearrangements upon further growth. An essential region for viability, at least in the absence of a 72-base-pair repeat, was revealed at the distal side of the 72-base-pair elements (L250 through L272). The effect of the deletions on Tantigen expression was measured, and the decreased viability of the mutants correlated with the impairment of T-antigen expression in all cases. The study of these mutants also revealed that the 72-base-pair repeats are not required for late transcription.