Finnish cell-phone titan

Nokia

(NOK) - Get Report

warned that a gush of new products will slacken its third-quarter earnings, and its shares

cratered in premarket trading. But you only own mutual funds, so what do you care? Right?

Wrong. If you're one of the more than four million investors who own shares of a

Janus

fund, you've got plenty of reason to care. That's because Janus has a

titanic bet on Nokia and the wireless communications sector.

At the end of the first quarter, Janus was far and away the largest institutional holder of Nokia, with a 5.7% stake in the company, according to

bigdough.com, a Web site that tracks institutional stock ownership. That's a $13.4 billion stake, which is more than No. 2 and No. 3 holders

AXA Financial

and

Fidelity

combined.

On April 30, the stock was the No. 1 holding in seven of Janus' 15 stock funds, and it appeared in 10 of Janus fund's top-10 holdings. It's impossible to say exactly how much Nokia Janus owns today because the top-selling Denver growth shop -- like most fund groups -- is secretive about its holdings. Indeed, Janus didn't immediately return a call this morning for comment. But a stake of that size isn't something that can be liquidated in a hurry.

Also, since telecommunications and semiconductors -- both relating to wireless communications bets -- are among the top five industries in most Janus stock funds, Nokia could send other Janus favorites up or down in sympathy.

Here's a list of the 10 funds with the biggest bets on Nokia. Note that two Janus funds made the list and

(SRGFX)

WM Growth is actually run by

(JAMRX) - Get Report

Janus Mercury manager Warren Lammert, according to

Morningstar

.

Before you panic, keep in mind that a shortfall for a big holding isn't reason to sell a fund. Also, at least one observer thinks Nokia's problems are short-term and investors' reactions are overblown.

"People selling right now should have their heads examined," says Morningstar stock analyst Todd Bernier. "It's a one-quarter problem. ... They're reporting 25% margins. Two weeks ago,

Motorola

(MOT)

pounded its chest over 4% margins. Nokia is just head and shoulders above everyone else."

Early in today's trading, Nokia was off more than 20%. But even with today's shortfall, Nokia has been a boon to Janus funds. Before today, the stock was up 15% for the year, and the stock has risen more than 200% in each of the past two calendar years.

Janus' big Nokia stake isn't just important for Janus shareholders. It's something Nokia investors should note, too. On one hand, they're probably excited that they hold a Janus favorite, which is akin to a seal of approval. After all, Janus has had an uncanny Midas touch for picking hot growth stocks in recent years. Last year, the firm's average stock fund posted an 81% gain.

"There are pluses and minuses to owning a stock with big institutional ownership. The plus is that some pretty sophisticated investors have done a lot of work and come to the same conclusion as you," says Tim Quinlisk who runs

(SPVAX)

John Hancock Small-Cap Value and

(TAGRX) - Get Report

John Hancock Large-Cap Value. "The minus is that they get information quicker than you and they might have a different time frame than you. They might decide that

the investment is dead money for a quarter or two. If they have a big stake, that can sink the stock."