We have cloned a human cDNA from a new gene, spi-B, on the basis of its homology with the DNA-binding domain of the Spi-l/PU.1 putative oncogene product. spi-B codes for a protein of 262 amino acids presenting 43% overall identity with Spi-1. Its highly basic carboxy-terminal region exhibits 34% sequence identity with the DNA-binding domain of the Ets-1 protein. We showed that the Spi-B protein is able to bind the purine-rich sequence (PU box) recognized by Spi-1/PU.A and to activate transcription of a reporter plasmid containing PU boxes. Chromosome in situ hybridization allowed us to map spi-B to the 19q13.3-19q13.4 region of the human genome. spi-B, like spi-1, was found to be expressed in various murine and human hematopoietic cell lines except T lymphoid cell lines.spi-1 is a putative oncogene involved in the malignant erythroblastic transformation induced by the acutely leukemogenic Friend and Rauscher spleen focus-forming viruses (25,26). It was originally identified as a genomic locus rearranged by spleen focus-forming proviral insertion in 95% of these tumors (25,27). The transcriptional deregulation of spi-1 by insertional mutagenesis results in overexpression of the Spi-1 protein (unpublished data). The product of spi-1 is identical to the PU.1 transcriptional activator (11) that recognizes specific DNA sequences characterized by a purine-rich core sequence, 5'-GAGGAA-3' (PU box), which acts as a Spi-l/PU.1-responsive element when linked in cis to the herpes simplex virus thymidine kinase promoter (18). The DNA-binding domain of Spi-1/PU.1 is localized to the carboxy-terminal half of the protein (18), a domain which includes a region of 87 amino acids related to that of the Ets proteins. The ets gene family includes c-ets-1 and c-ets-2 (5, 48, 49), erg (37), elk-1 and elk-2 (36), E74 (7), fli-i (2), elg (33), elf-I (45), and PEA3 (51) and encodes sequence-specific DNA-binding proteins. Ets-1 and Ets-2 (4, 12, 47), 38), Erg (42), and PEA3 (51) have been shown to act as transcriptional activators. c-ets-I is the cellular progenitor of the v-ets oncogene of E26 (20,29), a retrovirus which induces predominantly an erythroleukemia in chicken and transforms both myeloid and erythroid cells in vitro (35). In addition to v-ets, the E26 genome contains the v-myb oncogene, and both oncogenes are expressed as a nuclear Gag-Myb-Ets fusion protein (3).

Prototypical defective interfering (DI) RNAs of the plus-strand RNA virus tomato bushy stunt virus contain four noncontiguous segments (regions I-IV) derived from the viral genome. Region I corresponds to 5'-noncoding sequence, regions II and III are derived from internal positions, and region IV represents a 3'-terminal segment. We analyzed the internally located region III in a prototypical DI RNA to understand better its role in DI RNA accumulation. Our results indicate that (1) region III is not essential for DI RNA accumulation, but molecules that lack it accumulate at significantly reduced levels ( approximately 10-fold lower), (2) region III is able to function at different positions and in opposite orientations, (3) a single copy of region III is favored over multiple copies, (4) the stimulatory effect observed on DI RNA accumulation is not due to region III-mediated RNA stabilization, (5) DI RNAs lacking region III permit the efficient accumulation of head-to-tail dimers and are less effective at suppressing helper RNA accumulation, and (6) negative-strand accumulation is also significantly depressed for DI RNAs lacking region III. Collectively, these results support a role for region III as an enhancer-like element that facilitates DI RNA replication. A scanning-type mutagenesis strategy was used to define portions of region III important for its stimulatory effect on DI RNA accumulation. Interestingly, the results revealed several differences in the requirements for activity when region III was in the forward versus the reverse orientation. In the context of the viral genome, region III was found to be essential for biological activity. This latter finding defines a critical role for this element in the reproductive cycle of the virus.

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86As yet undiscovered rare variants are hypothesized to substantially influence an 87 individual's risk for common diseases and traits, but sequencing studies aiming to 88 identify such variants have generally been underpowered. In isolated populations that 89 have expanded rapidly after a population bottleneck, deleterious alleles that passed 90 through the bottleneck may be maintained at much higher frequencies than in other 91 populations. In an exome sequencing study of nearly 20,000 cohort participants from 92 northern and eastern Finnish populations that exemplify this phenomenon, most novel 93 trait-associated deleterious variants are seen only in Finland or display frequencies more 94 than 20 times higher than in other European populations. These enriched alleles underlie 95 34 novel associations with 21 disease-related quantitative traits and demonstrate a 96 geographical clustering equivalent to that of Mendelian disease mutations characteristic 97 of the Finnish population. Sequencing studies in populations without this unique history 98 would require hundreds of thousands to millions of participants for comparable power for 99 these variants. 100 101 (defined here as MAF≤1%) which are not well-tagged by the single-nucleotide 109 polymorphisms (SNPs) on genome-wide genotyping arrays are probably responsible for 110 much of the heritability that remains unexplained 2 . Additionally, because purifying 111 selection acts to remove deleterious alleles from the population, most variants that exert a 112 sizable effect on complex traits, and that likely offer the best prospect for revealing 113 biological mechanisms, should be particularly rare. 114 115 Rare variants are unevenly distributed between populations and difficult to represent 116 effectively on commercial genotyping arrays, as evidenced by relatively sparse 117 association findings even from large array-based studies of coding variants 3-6 . 118Discovering rare variant associations will therefore almost certainly require exome or 119 genome sequencing of very large numbers of individuals. However, the sample size 120 required to reliably identify rare-variant associations remains uncertain; most sequencing 121 studies to date have identified few novel associations, and theoretical analyses confirm 122 that they have been underpowered to do so 7 . These analyses also suggest that power to 123 detect rare variant associations varies enormously between populations that have 124 expanded in isolation from recent bottlenecks compared to those that have not. 125 126In isolated populations that expand rapidly following a bottleneck, alleles that pass 127 through the bottleneck often rise to a much higher frequency than in other populations [8][9][10] . 128If the bottleneck was recent, even deleterious alleles under negative selection may remain 129 relatively frequent in these populations, resulting in increased power to detect association 130 with disease-related traits. The Finnish population exemplifies this type of history. It 131 5 grew from bottle...

In Friend murine erythroleukemia cells, although no detectable c-myc gene rearrangement was found, we observed, in addition to the normal 2.3-kilobase c-myc transcript, the presence of a 2.3-kilobase c-myc mRNA initiated in intron 1 at a promoter site called P3. The intron 1-initiated transcript has a longer half-life than the normal c-myc mRNA. This c-myc transcript initiated in intron 1 was also found in other murine cell types where no rearrangement of the c-myc locus has been reported.