Multicellular living organisms and unmodified parts thereof and – Plant – seedling – plant seed – or plant part – per se
Patent
1995-12-15
2000-01-25
Kemmerer, Elizabeth
Multicellular living organisms and unmodified parts thereof and
Plant, seedling, plant seed, or plant part, per se
800278, 800279, 800286, 800289, 800298, 800300, 800301, 800302, 536 231, 536 236, 536 241, 435 691, 4353201, 435418, 435419, 435430, 4352523, A01H 500, C12N 121, C12N 510, C12N 1511
Patent
active
060181036
DESCRIPTION:
BRIEF SUMMARY
The present invention comes within the field of gene expression in plants and relates primarily to chimeric genes which contain an snRNA or mRNA promoter element and/or an snRNA 3' termination element from plants in functional combination with a structural gene, both elements being independent of each other in their function. In addition to this, the present invention relates to recombinant DNA vectors which comprise such chimeric gene constructs, and, furthermore, to microorganisms which harbour these vectors and to processes for preparing said chimeric gene constructs and vectors. Finally, the invention relates to plant cells, to parts of plants which can be regenerated to form whole and preferably fertile plants, and to the plants themselves including their descendents insofar as they express the chimeric genes according to the invention.
RNA polymerase II from eukaryotic cells transcribes two classes of genes: mRNA genes lead to the synthesis of mRNA, and snRNA genes to the synthesis of snRNA. The two classes of genes possess their own regulatory elements which differ from each other. The starting point or the initiation of transcription are determined and regulated by so-called promoter elements, and the end point of transcription or the formation of an intact RNA 3' end are signalled by so-called 3' termination elements.
In the cells of vertebrates, the 3' ends of the mRNA's are formed as a rule by endonucleolytic cleavage and subsequent polyadenylation of the primary RNA transcript. Here, the transcription for forming the primary transcript takes place first of all via a conserved AAUAAA hexanucleotide sequence and then via a subsequent G-U-rich or U-rich sequence. These two sequences are essential components of the so-called poly(A) signal that is responsible for the correct polyadenylation of the mRNA (Wahle and Keller, 1992).
Many yeast and plant mRNA's do not contain the hexanucleotide AAUAAA (Zaret and Sherman, 1984; Yu and Elder, 1989; Sanfacon et al., 1991; Mogen et al., 1992). However, it has been possible to show, using cell-free processing systems, that the mechanism of polyadenylation in yeast is analogous to the mechanism in vertebrate cells (Butler and Platt, 1988). The mechanism of polyadenylation of mRNA in plants is still not known.
In contrast to the formation of the 3' end of mRNA, formation of the 3' end of snRNA takes place simultaneously with transcription (Dahlberg and Lund, 1988; Hernandez and Lucito, 1988; Hernandez 1992). The site of transcription termination is signalled by the so-called 3' box, which is located beyond the gene sequence of the mature sRNA 3' end (Hernandez, 1985; Yuo et al, 1985).
It is a typical characteristic of all snRNA 3' termination elements in vertebrate cells that recognition of the 3' box signal is coupled to the initiation of transcription at the snRNA promoter element (Hernandez and Weiner, 1986; Neuman de Vegvar et al., 1986). This means that, in vertebrate cells, the promoter elements of snRNA genes also, at the same time, signal the formation of the correct 3' end. In the first place, these promoter elements contain approximately 200 bp of so-called "distal sequence elements" (DSE's) and approximately 60 bp of so-called "proximal sequence elements" (PSE's) prior to the transcription start point. In addition to this, these promoter elements are not able to initiate the transcription and synthesis of polyadenylated mRNA (Dahlberg and Schenborn, 1988). Due to these properties, snRNA genes cannot be expressed using an mRNA promoter element in vertebrate cells, for example.
It is known that an mRNA promoter element can successfully be used in yeast to transcribe an snRNA gene having a correct snRNA 3' end (Patterson and Guthrie, 1987). However, in yeast, the mRNA and snRNA promoters are virtually identical (Parker et al., 1988).
Plant snRNA genes, which are transcribed by RNA polymerase II, possess a 3' box having the consensus sequence CA(N).sub.1-3 AGTNNAA (Goodall et al., 1991) SEQ ID NO.: 16 immediately downstream of the coding region. An impor
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Connelly Sheila
Filipowicz Witold
Kemmerer Elizabeth
Novartis Finance Corporation
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