Fig. 8

a Dual-initiation promoters can be occupied by pre-initiation complexes (PIC) in a cell to generate two RNA products with distinct 5′ end base. These products can be produced on a shared promoter coordinately by partially overlapping PICs or by distinct PICs recruited coordinately. The co-regulation may occur on the cell or tissue level. b Model for differential utilization of YC and YR-initiation by divergent PICs to generate RNAs with distinct fate in the same or distinct cells. E.g. PICs form on the YR-initiation site for generating a protein coding mRNA or non-coding RNA gene product from a snoRNA host gene, while the YC-initiation may be utilized by a specialized PIC to produce an RNA which is processed to splice out snoRNAs and subjected to distinct degradation pathways. c A dual-initiation promoter is utilized divergently by YR and YC associated initiation complexes to adapt to requirements in different cells such as maternal activity in the oocyte versus zygotic activity in an embryonic cell.