Early embryonic germ cells in C. elegans and D. melanogaster fail to express many messenger RNAs expressed in somatic cells. In contrast, we find that ribosomal RNAs are expressed in both cell types. We show that this deficiency in mRNA production correlates with the absence of a specific phosphoepitope on the carboxy-terminal domain of RNA polymerase II. In both C. elegans and Drosophila embryos, this phosphoepitope appears in somatic nuclei coincident with the onset of embryonic transcription, but remains absent from germ cells until these cells associate with the gut primordium during gastrulation. In contrast, a second distinct RNA polymerase II phosphoepitope is present continuously in both somatic and germ cells. The germ-line-specific factor PIE-1 is required to block mRNA production in the germ lineage of early C. elegans embryos (Seydoux, G., Mello, C. C., Pettitt, J., Wood, W. B., Priess, J. R. and Fire, A. (1996) Nature 382, 713–716). We show here that PIE-1 is also required for the germ-line-specific pattern of RNA polymerase II phosphorylation. These observations link inhibition of mRNA production in embryonic germ cells to a specific modification in the phosphorylation pattern of RNA polymerase II and suggest that repression of RNA polymerase II activity may be part of an evolutionarily conserved mechanism that distinguishes germ line from soma during early embryogenesis. In addition, these studies also suggest that different phosphorylated isoforms of RNA polymerase II perform distinct functions.

REFERENCES

REFERENCES
Albertson
D. G.
(
1984
)
Localization of ribosomal genes in Caenorhabditis elegans chromosomes by in situ hybridization using biotin-labeled probes.
EMBO J
3
,
1227
1234
Bai
C.
,
Tolias
P. P.
(
1996
)
Cleavage of RNA hairpins mediated by a developmentally regulated CCCH zinc finger protein.
Mol. Cell. Biol
16
,
6661
6667
Bird
D. M.
,
Riddle
D. L.
(
1989
)
Molecular cloning and sequencing of ama-1, the gene encoding the largest subunit of Caenorhabditis elegans RNA polymerase II.
Mol. Cell. Biol
9
,
4119
4130
Bregman
D. B.
,
Du
L.
,
van der Zee
S.
,
Warren
S. L.
(
1995
)
Transcription dependent redistribution of the large subunit of RNA polymerase II to discrete nuclear domains.
J. Cell Biol
129
,
287
298
Brenner
S.
(
1974
)
The genetics of Caenorhabditis elegans.
Genetics
77
,
71
94
Dahmus
M. E.
(
1996
)
Reversible phosphorylation of the C-terminal domain of RNA polymerase II.
J. Biol. Chem
271
,
19009
19012
DuBois
R. N.
,
McLane
M. W.
,
Ryder
K.
,
Lau
L. F.
,
Nathans
D.
(
1990
)
A growth factor-inducible nuclear protein with a novel cysteine/histidine repetitive sequence.
J. Biol. Chem
265
,
19185
19191
Edgar
B. A.
,
Schubiger
G.
(
1986
)
Parameters controlling transcriptional activation during early Drosophila development.
Cell
44
,
871
877
Emmons
S.W.
,
Klass
M.R.
,
Hirsh
D.
(
1979
)
Analysis of the constancy of DNA sequences during development and evolution of the nematode C. elegans.
Proc. Natn. Acad. Sci. USA
76
,
1333
1337
Guo
S.
,
Kemphues
K. J.
(
1995
)
par-1, a gene required for establishing polarity in C. elegans embryos, encodes a putative Ser/Thr Kinase that is asymmetrically distributed.
Cell
81
,
1
20
Hay
B.
,
Jan
L.Y.
,
Jan
Y. N.
(
1990
)
Localization of Vasa, a component of Drosophila polar granules, in maternal effect mutants that alter embryonic anteroposterior polarity.
Development
109
,
425
433
Kim
E.
,
Du
L.
,
Bregman
D. B.
,
Warren
S. L.
(
1997
)
Splicing factors associate with hyperphosphorylated RNA polymerase II in the absence of pre-mRNA.
J. Cell Biol
136
,
19
28
Kobayashi
S.
,
Mizuno
H.
,
Okada
M.
(
1988
)
Accumulation and spatial distribution of poly-A+ RNA in oocytes and early embryos of Drosophila melanogaster.
Develop. Growth and Differ
30
,
251
260
Kobayashi
S.
,
Yamada
M.
,
Asaoka
M.
,
Kitamura
T.
(
1996
)
Essential role of the posterior morphogen nanos for germline development in Drosophila.
Nature
380
,
709
711
Lamb
M. M.
,
Laird
C. D.
(
1976
)
Increase in nuclear poly(A)-containing RNA at syncytial blastoderm in Drosophila melanogaster embryos.
Dev. Biol
54
,
31
42
Lasko
P. F.
,
Ashburner
M.
(
1990
)
Posterior localization of vasa protein correlates with, but is not sufficient for, pole cell development.
Genes Dev
4
,
905
921
Mello
C. C.
,
Kramer
J. M.
,
Stinchcomb
D.
,
Ambros
V.
(
1991
)
Efficient gene transfer in C. elegans: extrachromosomal maintenance and integration of transforming sequences.
EMBOJ
10
,
3959
3970
Mello
C. C.
,
Draper
B. W.
,
Krause
M.
,
Weintraub
H.
,
Priess
J.
(
1992
)
The pie-1 and mex-1 genes and maternal control of blastomere identity in early C. elegans embryos.
Cell
70
,
163
176
Mello
C. C.
,
Schubert
C.
,
Draper
B.
,
Zhang
W.
,
Lobel
R.
,
Priess
J. R.
(
1996
)
The PIE-1 protein and germline specification in C. elegans embryos.
Nature
382
,
710
712
Mohler
J.
,
Weiss
N.
,
Murli
S.
,
Mohammadi
S.
,
Vani
K.
,
Vasilakis
G.
,
Song
C. H.
,
Epstein
A.
,
Kuang
T.
,
English
J.
,
Cherdak
D.
(
1992
)
The embryonically active gene, unkempt, of Drosophila encodes a Cys3His finger protein.
Genetics
131
,
377
388
Powell-Coffman
J. A.
,
Knight
J.
,
Wood
W. B.
(
1996
)
Onset of C. elegans gastrulation is blocked by inhibition of embryonic transcription with an RNA polymerase antisense RNA.
Dev. Biol
178
,
472
483
Reuter
R.
,
Panganiban
G.E.F.
,
Hoffmann
F.M.
,
Scott
M.P.
(
1990
)
Homeotic genes regulate the spatial expression of putative growth factors in the visceral mesoderm of Drosophila embryos.
Development
110
,
1031
1040
Sanford
T.
,
Prenger
J. P.
,
Golomb
M.
(
1985
)
Purification and immunological analysis of RNA polymerase II from Caenorhabditis elegans.
J. Biol. Chem
260
,
8064
8069
Seydoux
G.
,
Fire
A.
(
1994
)
Soma-germline asymmetry in the distribution of embryonic RNAs in C. elegans embryos.
Development
120
,
2823
2834
Seydoux
G.
,
Mello
C. C.
,
Pettitt
J.
,
Wood
W. B.
,
Priess
J. R.
,
Fire
A.
(
1996
)
Repression of gene expression in the embryonic germ lineage of C. elegans.
Nature
382
,
713
716
Strome
S.
(
1986
)
Asymmetric movements of cytoplasmic components in Caenorhabditis elegans zygotes.
J. Embryol. Exp. Morph
97
,
15
29
Sulston
J. E.
,
Schierenberg
E.
,
White
J. G.
,
Thomson
J. N.
(
1983
)
The embryonic cell lineage of the nematode C. elegans.
Dev. Biol
100
,
64
119
Tautz
D.
,
Hancock
J. M.
,
Webb
D. A.
,
Tautz
C.
,
Dover
G. A.
(
1988
)
Complete sequences of the rRNA genes of Drosophila melanogaster.
Mol. Biol. Evol
5
,
366
376
Tautz
D.
,
Pfeifle
C.
(
1989
)
A nonradioactive in situ hybridization methodfor the localization of specific RNAs in Drosophila embryos reveals translational control of the segmentation gene hunchback.
Chromosoma
98
,
81
85
Vanfleteren
J. R.
,
Van de Peer
Y.
,
Blaxter
M. L.
,
Tweedie
S. A. R.
,
Trotman
C.
,
Lu
L.
,
Van Hauwaert
M. L.
,
Moens
L.
(
1994
)
Molecular genealogy of some nematode taxa as based on cytochrome c and globin amino acid sequences.
Mol. Phylogenet. Evol
3
,
2
–.
Varnum
B. C.
,
Ma
Q. F.
,
Chi
T. H.
,
Fletcher
B.
,
Herschman
H. R.
(
1991
)
The TIS11 primary response gene is a member of a gene family that encodes proteins with a highly conserved sequence containing an unusual Cys-His repeat.
Mol. Cell Biol
11
,
1754
1758
Voelker
R. A.
,
Gibson
W.
,
Graves
J. P.
,
Sterling
J. F.
,
Eisenberg
M. T.
(
1991
)
The Drosophilasuppressor of sable gene encodes a polypeptide with regions similar to those of RNA-binding proteins.
Mol. Cell Biol
11
,
894
905
Wang
C.
,
Dickinson
L. K.
,
Lehmann
R.
(
1994
)
Genetics of nanos localization in Drosophila.
Dev. Dynamics
199
,
103
115
Warren
S. L.
,
Landolfi
A. S.
,
Curtis
C.
,
Morrow
J. S.
(
1992
)
Cytostellin: a novel highly conserved protein that undergoes continuous redistribution during the cell cycle.
J. Cell Sci
103
,
381
388
Weeks
J. R.
,
Coulter
D. E.
,
Greenleaf
A. L.
(
1982
)
Immunological studies of RNA polymerase II using antibodies to subunits of Drosophila and wheat germ enzyme.
J. Biol. Chem
257
,
5884
5892
Williamson
A.
,
Lehmann
R.
(
1996
)
Germ cell development in Drosophila.
Annu. Rev. Cell. Dev. Biol
12
,
365
391
Yuryev
A.
,
Corden
J. L.
(
1996
)
Suppression analysis reveals a functional difference between the serines in position two and five in the consensus sequence of the C-terminal domain of yeast RNA polymerase II.
Genetics
143
,
661
671
Zalokar
M.
(
1976
)
Autoradiographic study of protein and RNA formation during early development of Drosophila eggs.
Dev. Biol
49
,
425
437
Zhang
M.
,
Zamore
P. D.
,
Carmo-Fonseca
M.
,
Lamond
A. I.
,
Green
M. R.
(
1992
)
Cloning and intracellular localization of the U2 small nuclear ribonucleoprotein auxiliary factor small subunit.
Proc. Natl Acad. Sci. USA
89
,
8769
8773
This content is only available via PDF.