Regulation of c-mos transcription

It should be noted that the NRE defined in these experiments is distinct from the previously described c-mos UMS sequence (Blair et al., 1984 Wood et al., 1984). The UMS is located approximately 1.4 kb upstream of the c-mos spermatocyte promoter and was identified because it blocked activation of c-mos transforming potential by insertion of retroviral promoters. It is thought to act as a transcriptional terminator, blocking transcription of c-mos initiated at upstream sequences. However, both the spermatocyte and oocyte transcription initiation sites are substantially downstream of the UMS. Moreover, the presence or absence of the UMS does not affect c-mos expression in either microin-jected oocytes (Pal et al., 1991) or transfected NIH 3T3 cells (Zinkel et al., 1992). It thus appears unlikely that the UMS functions as a negative regulator of c-mos transcription from either the spermatocyte or oocyte promoters in somatic cells. 

The highly restricted tissue-specific transcription of c-mos poses an interesting problem in gene regulation during germ cell development. Moreover, c-mos is transcribed from different promoters in mouse spermatocytes and oocytes (Fig. 4) (Propst et al., 1987). In spermatocytes, transcription initiates approximately 280 nucleotides upstream of the c-mos ATG (Propst et al., 1987), whereas the transcription start site in oocytes has been mapped to 53 base pairs upstream of the ATG (Pal et al., 1991). Neither the spermatocyte nor oocyte promoter regions are... 

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