Science - USA (2018-12-21)

sciencemag.org SCIENCE

RESEARCH

CELL BIOLOGY

Protecting the heart
Excitation-contraction (E-C)
coupling is fundamental to heart
contraction. Junctophilin-2 is a
structural protein required for
formation of the E-C coupling
machinery. During heart disease,
stress-activated calpain cleaves
junctophilin-2, disrupting the E-C
coupling machinery and calcium
ion signaling, which compromises
cell contraction. Guo et al. found
that under stress conditions,
calpain-mediated cleavage con-
verted full-length junctophilin-2
from a structural protein into a
transcriptional regulator that
shuttled to the nucleus (see the
Perspective by Padmanabhan
and Haldar). Furthermore, failing
cardiomyocytes in stressed myo-
cardium transduced mechanical
information (E-C uncoupling) into
transcriptional reprogramming.
—BAP
Science, this issue p. 1375;
see also p. 1359

STRUCTURAL BIOLOGY

Mechanism of promoter

recognition
To start transcription, RNA
polymerase II is recruited by the
general transcription factor IID
(TFIID) to the DNA promoter.
Patel et al. used a combination
of experimental approaches
to elucidate the full molecular
architecture of human TFIID and
its complete conformational
landscape during promoter rec-
ognition. They suggest exactly
how TFIID is loaded onto the
promoter, which involves defined
steps—including promoter
recognition and transcription
initiation—and leads to regulated
gene expression. —SYM
Science, this issue p. 1376

STRUCTURAL BIOLOGY

Architecture of the

human TRPM2 channel
Adenosine diphosphate–ribose
(ADPR) mediates calcium (Ca2+)

release by activating the

transient receptor potential

melastatin 2 (TRPM2) channel.

Three structures now elucidate

the conformational regulation

mechanism of TRPM2 gating.

Wang et al. describe cryo–elec-

tron microscopy structures

of human TRPM2 in the apo,

ADPR-bound, and ADPR- and

Ca2+-bound states. In the apo

state, both intra- and intersub-

unit interactions appeared to

lock TRPM2 into a closed and

autoinhibited state. ADPR bind-

ing disrupted some interactions

and dramatically altered the

TRPM2 conformation. Binding of

Ca2+ further primed the opening

of the channel. —SYM

Science, this issue p. 1377

MOLECULAR MAGNETS

Cobalt unfettered by its

ligand field

Applied magnetic fields induce

a field in any compound with

unpaired electrons. However,

for the induced field to persist

once the applied field is gone,

the electrons must be config-

ured to manifest orbital angular

momentum. Generally, the influ-

ence of ligands severely restricts

that property in transition metal

complexes. Bunting et al. now

show that a cobalt ion is just

barely affected by two linearly

coordinated carbon ligands and,

as such, exhibits maximal orbital

angular momentum. Although its

magnetic properties mainly per-

tain at very low temperature, its

structure offers a more general

design principle. —JSY

Science, this issue p. 1378

CRITICAL TRANSITIONS

Cascading effects of

regime shifts

The potential for regime shifts

and critical transitions in

ecological and Earth systems,

particularly in a changing climate,

has received considerable atten-

tion. However, the possibility of

interactions between such shifts

is poorly understood. Rocha et al.

used network analysis to explore

whether critical transitions in

ecosystems can be coupled with

each other, even when far apart

(see the Perspective by Scheffer

and van Nes). They report differ-

ent types of potential cascading

effects, including domino effects

and hidden feedbacks, that can

be prevalent in different systems.

Such cascading effects can

couple the dynamics of regime

shifts in distant places, which

suggests that the interactions

between transitions should be

borne in mind in future forecasts.

—AMS and BJ

Science, this issue p. 1379;

see also p. 1357

GUT MICROBES

Distinguishing two similar

gut disorders

Inflammatory bowel disease and

irritable bowel syndrome are two

of the most common diseases

of the gastrointestinal tract. Vich

Vila et al. characterized the gut

microbe composition of both

disorders using shotgun metage-

nomic sequencing of stool

samples from 1792 individuals.

Bacterial taxonomy, metabolic

functions, antibiotic resistance

genes, virulence factors, and

bacterial growth rates revealed

key differences between these

two gut disorders. —OMS

Sci. Transl. Med. 10 , eaap8914 (2018).

PLASMA ASTROPHYSICS

Reconnection in Earth’s

magnetotail

Magnetic fields in plasmas

can rapidly rearrange them-

selves in a process known as

magnetic reconnection, which

releases energy and acceler-

ates particles. Torbert et al. used

the Magnetospheric Multiscale

(MMS) mission to probe a

reconnection event in Earth’s

magnetotail—the region of

plasma downstream from the

planet as it moves through the

solar wind. MMS has previously

studied reconnection in the

upstream magnetopause, but

a different orbit was used to

study the magnetotail, where

the symmetry of the process is

different. The authors measured

plasma properties on scales of

the electron dynamics, leading

to insights that will apply in other

regions where magnetic recon-

nection occurs. —KTS

Science, this issue p. 1391

PALEOBOTANY

Late Permian seed-plant

evolution

The great evolutionary expan-

sion of seed plants took place

in the Mesozoic era, which

began after the Permian mass

extinction 252 million years ago.

Blomenkemper et al. report the

discovery of seed-plant fossils

from Late Permian (252-mil-

lion- to 260-million-year-old)

deposits on the margins of the

Dead Sea in Jordan. This area

represents an equatorial habitat

with pronounced dry seasons.

These fossils, which include the

earliest records of conifers, push

back the ages of several impor-

tant seed-plant lineages. Some

of these lineages appear to span

the mass extinction event at

the end of the Permian, which

suggests that the communi-

ties they supported may have

been more stable than expected

over this tr ansition. Thus, early

evolutionary innovations can

occur in drought-prone tropical

habitats—which rarely offer

the conditions needed for fossil

preservation. —AMS

Science, this issue p. 1414

PAIN

A painful lipid in irritable

bowel syndrome

Patients with irritable bowel

syndrome (IBS) often experi-

ence abdominal pain. Bautzova

et al. found that the abundance

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1374-B 21 DECEMBER 2018 • VOL 362 ISSUE 6421

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